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Chapter 7Chapter 7

Atomic StructureAtomic Structure pp pp

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7.1 Electromagnetic Radiation7.1 Electromagnetic Radiation LightLight is made up of is made up of electromagnetic electromagnetic

radiationradiation.. Waves of electric and magnetic fields at Waves of electric and magnetic fields at

right anglesright angles to each other. to each other. LD 1: 4-1 Electromagnetic radiationLD 1: 4-1 Electromagnetic radiation

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Electromagnetic RadiationMutually propagating electric and magnetic fields, at right angles to each other, traveling at the speed of light c

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Parts of a wave

Wavelength

AmplitudeOrigin

Crest

Trough

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Parts of Wave Origin - the base line of the energy. Crest - high point on a wave Trough - Low point on a wave Amplitude - distance from origin to crest Wavelength - distance from crest to

crest Wavelength - is abbreviated Greek

letter lambda.

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Parts of a waveParts of a wave

Wavelength

Frequency = number of cycles in one secondMeasured in hertz 1 hertz = 1 cycle/second

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Frequency The number of waves that pass a

given point per second. Units are cycles/sec or hertz (Hz) Abbreviated the Greek letter nu

c =

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Frequency and wavelength Are inversely related As one goes up the other goes down. Speed is constant! (Tricky) In a vacuum it is 3.00 x 108 m/s or 3.00 x 1010 cm/s Memorize both. Also, 1 m = 1 x 109 nm = 1 x 1010 Å

(angstrom)

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Frequency = Frequency =

Figure 7.1The Nature of Waves

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Kinds of EM waves Kinds of EM waves There are many There are many different different and and Radio waves, microwaves, x rays Radio waves, microwaves, x rays

and gamma rays are all examples.and gamma rays are all examples. Light is only the part our eyes can Light is only the part our eyes can

detect.detect.

GammaRays

Radiowaves

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Radio waves

Microwaves

Infrared .

Ultra-violet

X-Rays

Gamma Rays

Low energy

High energy

Low Frequency

High Frequency

Long Wavelength

Short WavelengthVisible Light

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Electromagnetic Spectrum

Which has longer , ultraviolet or gamma rays?UV rays

Which has shorter wavelength, microwave or infrared?

Microwave

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Figure 7.2Figure 7.2Classification of Electromagnetic RadiationClassification of Electromagnetic Radiation

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The speed of lightThe speed of light In a vacuum is 2.998 x 10In a vacuum is 2.998 x 1088 m/s = c m/s = c cc = = What is the What is the wavelengthwavelength of light with a of light with a

frequencyfrequency 5.89 x 10 5.89 x 1055 Hz? Ans . . . Hz? Ans . . . 509 m509 m (using 2.998 x 10 (using 2.998 x 1088m/s)m/s) What is the What is the frequencyfrequency of blue light with of blue light with

a a wavelengthwavelength of of 484 nm484 nm?? 6.19 x 106.19 x 101414 Hz Hz

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7.2 The Nature of Matter7.2 The Nature of Matter In 1900In 1900 Matter and energy were seen as Matter and energy were seen as

different from each other in fundamental different from each other in fundamental ways.ways.

It was thought that matter was particles.It was thought that matter was particles. It was thought that energy could come in It was thought that energy could come in

waves, waves, with any frequencywith any frequency.. Max Planck found the cooling of hot objects Max Planck found the cooling of hot objects

could could notnot be explained by viewing energy be explained by viewing energy as a wave. as a wave.

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The Photoelectric Effect Photoelectric Effect - the emission of

electrons from a metal when light shines on it.

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Tr 19 Fig 4.3 p. 93 Photoelectric Effect

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The Photoelectric Effect Problem What was predicted . . .

Wave theory said light of any would have

enough energy to eject an electrons. What was observed . . .

For a given metal, no e- are emitted if is

below a certain frequency no matter how long the light shines.

The explanation . . .

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Light is a Particle as well as a Wave

Energy is quantized. Light is energy Light must be quantized These smallest pieces of light are

called photons. Energy and frequency are directly

related.

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Energy is QuantizedEnergy is Quantized Planck found Planck found E came in chunks with size E came in chunks with size

hh E = nhE = nh where n is an integerwhere n is an integer and h is and h is Planck’s constantPlanck’s constant h = 6.626 x 10h = 6.626 x 10-34-34 J•s J•s 1 joule = 1 Kg m1 joule = 1 Kg m22/s/s22 (know this!) (know this!) these packets of hthese packets of h are called are called quanta quanta

(singular = quantum)(singular = quantum)

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Einstein is nextEinstein is next He said electromagnetic radiation is He said electromagnetic radiation is

quantizedquantized in particles called in particles called photonsphotons.. Each photon has energy E= hEach photon has energy E= h = = hc/hc/ Combine this with E = Combine this with E = mcmc22

mcmc22 = = hc/hc/ You get the You get the apparentapparent mass mass of a photon. of a photon. mm = h / ( = h / (c)c)

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Which is Energy?Which is Energy? Is energy a wave like light, or a particle?Is energy a wave like light, or a particle? Both. Both. Concept is called the Wave-Particle Concept is called the Wave-Particle

duality.duality. What about the other way, is matter a What about the other way, is matter a

wave? wave? YesYes

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Figure 7.4Figure 7.4Electromagnetic RadiationElectromagnetic Radiation

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Matter as a waveMatter as a wave Using the velocity v instead of the Using the velocity v instead of the

speed of light c we get. . . speed of light c we get. . . De Broglie’s equation De Broglie’s equation = h/mv = h/mv Mass in this equation is in Mass in this equation is in kgkg (not g!) (not g!) Remember this! You have an online Remember this! You have an online

HW question that uses this equation.HW question that uses this equation. Can calculate the wavelength of an Can calculate the wavelength of an

object.object.

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ExamplesExamples pppp

The laser light of a CD player is 7.80 x 10The laser light of a CD player is 7.80 x 102 2 m. m. What is the What is the frequencyfrequency? Answer . . .? Answer . . .

C = C = so so = c/ = c/ = = 3.84 x 103.84 x 1055 Hz Hz What is the What is the energyenergy of a photon of this light? of a photon of this light? E = hE = h E = 2.55 x 10E = 2.55 x 10-28-28 J J What is the apparent mass for this photon?What is the apparent mass for this photon? apparent mass = h/ apparent mass = h/ c = 2.83 x10c = 2.83 x10-45 -45 kgkg What is the energy of a mole of photons?What is the energy of a mole of photons? E of mole in (c) above = (h/E of mole in (c) above = (h/ c) x Avogadro's c) x Avogadro's

number = 1.54 x 10number = 1.54 x 10-4-4 J/mol J/mol

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What is the wavelength?What is the wavelength?

Of an electron with a mass of 9.11 x 10Of an electron with a mass of 9.11 x 10-31-31 kg kg

traveling at 1.0 x 10traveling at 1.0 x 1077 m/s? Note: all em/s? Note: all e--s have s have same mass & 1 joule = 1 Kg msame mass & 1 joule = 1 Kg m22/s/s22 Use Use = h/mv to get . . .= h/mv to get . . .

7.27 x 107.27 x 10-11-11m for the electronm for the electron Of a softball with a mass of 0.10 kg moving at Of a softball with a mass of 0.10 kg moving at

125125 mi/hrmi/hr? ? Same equation to get . . .Same equation to get . . . 1.9 x 101.9 x 10-34-34m for the ball (Compare to electron)m for the ball (Compare to electron)

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DiffractionDiffraction When light passes through, or reflects When light passes through, or reflects

off, a series of thinly spaced lines, it off, a series of thinly spaced lines, it creates a rainbow effect. creates a rainbow effect.

This is because the waves This is because the waves interfereinterfere with with each other. each other.

LD 1: 4.14LD 1: 4.14

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A wave moves toward a slit.

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Comes out as a curve

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with two holes

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with two holes Two Curves

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Two Curveswith two holes

Interfere with each other

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Two Curveswith two holes

Interfere with each other

crests add up

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Several waves

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Several wavesSeveral Curves

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Several wavesSeveral waves

Interference Pattern

Several Curves

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What will an electron do if diffracted?What will an electron do if diffracted?

It has It has massmass, so it is matter., so it is matter. A A particleparticle can only go through can only go through oneone hole. hole. A A wavewave can go through can go through bothboth holes. holes. An An electronelectron does go though both, and does go though both, and

makes an makes an interference patterninterference pattern.. It behaves like a wave.It behaves like a wave. Other matter have wavelengths too Other matter have wavelengths too

short to notice.short to notice.

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Figure 7.5 The Constructive and Figure 7.5 The Constructive and

Destructive Interference of WavesDestructive Interference of Waves

a.a. Diffraction occurs when Diffraction occurs when electromagnetic radiation is electromagnetic radiation is scatteredscattered from a regular array from a regular array such as NaCl crystals.such as NaCl crystals.

b.b. Bright spotsBright spots from from constructiveconstructive interference of waves.interference of waves.

c.c. Dark areasDark areas from from destructive destructive interference.interference.

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SpectrumSpectrum The range of frequencies present in The range of frequencies present in

light.light. White light has a continuous White light has a continuous

spectrum.spectrum. All the colors are possible.All the colors are possible. A rainbow.A rainbow.

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Figure 7.6Figure 7.6A Continuous A Continuous Spectrum (a) and Spectrum (a) and A Hydrogen Line A Hydrogen Line Spectrum (b)Spectrum (b)

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7.3 Atomic Spectrum of Hydrogen Emission spectrum because these are the

colors it gives off or emits. LD1: 4.7 Called a line spectrum. Each element has

a unique one. Like a fingerprint. There are just a few discrete lines showing

410 nm

434 nm

486 nm

656 nm

Line emission spectra of H, Hg, and Ne

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What this means

Only certain energies are allowed for the electron in an hydrogen atom.

Can only give off certain energies. Use E = h= hc / Energy in the in the atom is

quantized. This is where we get quantum theory.

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7.4 The Bohr Model Niels Bohr developed the quantum model of

the hydrogen atom. He said electrons move like planets

around the sun (later found incomplete).

Only works for hydrogen electron & other monoelectronic species (e.g., He1+ ion).

The electrons were attracted to the nucleus because of opposite charges.

Did not fall in to the nucleus because they were moving around very rapidly.

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The Bohr Ring Atom He didn’t know why but only certain

energies were allowed. He called these allowed energies energy

levels. Putting energy into the atom moved the

electron away from the nucleus. From ground state to excited state. When it returns to ground state it gives off

light of a certain energy. LD 1: 4.9

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The Bohr Ring Atom

n = 3n = 4

n = 2n = 1

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The Bohr ModelThe Bohr Model n is the energy leveln is the energy level for each energy level the energy is:for each energy level the energy is: E = -2.178 x 10E = -2.178 x 10-18-18 J (ZJ (Z22 / n / n22 ) ) Z is the nuclear charge, which is +1 Z is the nuclear charge, which is +1

for hydrogen (+2 for Hefor hydrogen (+2 for He11+ ion, etc.).+ ion, etc.). n = 1 is called the ground staten = 1 is called the ground state when the electron is removed, n = ∞when the electron is removed, n = ∞ E = 0E = 0

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We are worried about the change We are worried about the change When the electron moves from one When the electron moves from one

energy level to another in an H atom energy level to another in an H atom (I.e., Z = 1).(I.e., Z = 1).

E = EE = Efinal final - E- Einitialinitial

E = -2.178 x 10E = -2.178 x 10-18-18 J Z J Z22 (1/ n (1/ nff22 - 1/ n - 1/ nii

22))

Use for monoelectronic species onlyUse for monoelectronic species only

(e.g. He(e.g. He1+1+ ion) ion)

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Examples if timeExamples if timeE = -2.178 x 10E = -2.178 x 10-18-18 J Z J Z22 (1/ n (1/ nff

22 - 1/ n - 1/ nii22))

Calculate the energy needed to move a hydrogen Calculate the energy needed to move a hydrogen electron from its first level to the third energy electron from its first level to the third energy level. Ans. . .level. Ans. . .

1.936 x 101.936 x 10-18-18 Joules Joules Calculate the E released when an electron Calculate the E released when an electron

moves from n= 4 to n=2 in a hydrogen atom.moves from n= 4 to n=2 in a hydrogen atom. -4.084 x 10-4.084 x 10-19-19 Joules (negative value means Joules (negative value means

energy energy releasedreleased)) Calculate the E released when an e- moves from Calculate the E released when an e- moves from

n= 5 to n=3 in a Hen= 5 to n=3 in a He+1+1 ionion ( (monoelectronic speciesmonoelectronic species)) -6.195 x 10-6.195 x 10-19-19 Joules (negative value means Joules (negative value means

energy energy releasedreleased))

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When is it true?When is it true? OnlyOnly for hydrogen atoms and other for hydrogen atoms and other

monoelectronic species.monoelectronic species. Why the negative sign?Why the negative sign? To decrease the energy of the electron To decrease the energy of the electron

(i.e., the system) you make it closer to (i.e., the system) you make it closer to the nucleus.the nucleus.

the maximum energy an electron can the maximum energy an electron can have is zero, at an infinite distance. have is zero, at an infinite distance.

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When is it true?When is it true?a.a. Model correctly fits the quantitized energy Model correctly fits the quantitized energy

levels of levels of H atomH atom and postulates and postulates only certain only certain allowed circular orbitsallowed circular orbits for the electron. for the electron.

b.b. As e- becomes more As e- becomes more tightlytightly bound, its bound, its energy becomes energy becomes more negativemore negative relative to relative to the zero-energy reference state the zero-energy reference state (corresponding to the e- being at infinite (corresponding to the e- being at infinite distance from the nucleus). distance from the nucleus). As e- is brought As e- is brought closer to nucleus, energy is closer to nucleus, energy is releasedreleased from from the system.the system.

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Bohr’s ModelBohr’s ModelIn

crea

sing

ene

rgy

Nucleus

First

Second

Third

Fourth

Fifth

} Further away Further away

from the from the nucleus means nucleus means more energy.more energy.

There is no “in-There is no “in-between” between” energyenergy

Energy LevelsEnergy Levels

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The Bohr Model

Doesn’t work generally. Only works for hydrogen atoms (and

other monoelectronic species). Electrons do not move in circles. The energy quantization is right, but

not because they are circling like planets.

So, we need another model (LD 4.12)

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7.5 The Quantum Mechanical Model7.5 The Quantum Mechanical Model

A totally new approach.A totally new approach. De Broglie said matter could be like a De Broglie said matter could be like a

wave.wave. De Broglie said they were like standing De Broglie said they were like standing

waves.waves. The vibrations of a stringed instrument.The vibrations of a stringed instrument.

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Standing Waves - fixed or “quantized” wavelengths, d = n(/2)

nodes

d = (1/2)

d =

d = (3/2)

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Figure 7.9Figure 7.9The Standing Waves The Standing Waves Caused by the Vibration of Caused by the Vibration of a Guitar String Fastened at a Guitar String Fastened at Both Ends.Both Ends. Each dot represents a node Each dot represents a node (a point of zero (a point of zero displacement).displacement).

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What’s possible? You can only have a standing wave if you

have complete waves (standing wave generator demo).

There are only certain allowed waves. In the atom there are certain allowed waves

called electrons. 1925 Erwin Schrödinger described the

wave function of the electron. Much math but what is important are the

solutions.

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Figure 7.10Figure 7.10The Hydrogen Electron The Hydrogen Electron Visualized as a Standing Wave Visualized as a Standing Wave Around the NucleusAround the Nucleus

Destructive interference occurs Destructive interference occurs if orbit does not equal a if orbit does not equal a complete wave.complete wave.

So only certain electron So only certain electron energies are allowed.energies are allowed.

“allowed” orbit = constructive interference

“forbidden” orbit = destructive interference

Standing Waves

E. Schrödinger (1927)

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The Schrodinger Wave Equation

Energy is quantized. It comes in chunks. A quanta is the amount of energy needed to

move from one energy level to another. Since the energy of an atom is never “in-

between” there must be a quantum leap in energy.

Schrodinger derived an equation that described the energy and probable position of the electrons in an atom.

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Schrödinger’s Equation The wave function is a F(x, y, z) Solutions to the equation are called

orbitals. These are not Bohr orbits. Each solution is tied to a certain energy. These are the energy levels.

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There is a limit to what we can There is a limit to what we can knowknow

We can’t know how the electron is We can’t know how the electron is moving or how it gets from one energy moving or how it gets from one energy level to another.level to another.

The Heisenberg Uncertainty Principle.The Heisenberg Uncertainty Principle. There is a limit to how well we can know There is a limit to how well we can know

both the position and the momentum of both the position and the momentum of an object.an object.

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Heisenberg Uncertainty Principle

It is impossible to know exactly the position and velocity of a particle at the same time.

The better we know one, the less we know the other.

The act of measuring changes the properties.

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More obvious with the very small

To measure where a electron is, we use light. But the light moves the electron And hitting the electron changes the frequency of the

light. Both the electron and the light are changed by the

collision. Light photons are too small to affect anything other than

electrons in the manner.

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Moving Electron

Photon

Before

ElectronChanges velocity

Photon changes wavelength

After

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MathematicallyMathematically x · x · (mv) > h/4(mv) > h/4 x is the uncertainty in the position.x is the uncertainty in the position. (mv) is the uncertainty in the (mv) is the uncertainty in the

momentum.momentum. the minimum uncertainty is h/4the minimum uncertainty is h/4

We can never SIMULTANEOUSLY know with absolute precision both the exact position (x), and momentum (mass X velocity or mv), of the electron.

x • (mv) > hUncertainty in momentum

Uncertainty in position

Planck’s constant

If one uncertainty gets very small, then the other becomes very large

If an electron is moving at 1.0 X 108 m/s with an uncertainty in velocity of 0.10 %, then what is the uncertainty in position?

x • (mv) > h and rearranging

x > h / (mv) or since the mass is fixed

x > h / mv

x > 7.3 X 10-9 m or 7300 pm

x > (6.63 X 10-34 Js) (9.11 X 10-31 kg)(.001 X 1 X 108 m/s)

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Examples - Plug & ChugExamples - Plug & ChugWe’ll skip the problems, know the conceptWe’ll skip the problems, know the concept

What is the uncertainty in the position of What is the uncertainty in the position of an electron. mass 9.31 x 10an electron. mass 9.31 x 10--3131 kg with kg with an uncertainty in the speed of .100 m/san uncertainty in the speed of .100 m/s

What is the uncertainty in the position of What is the uncertainty in the position of a baseball, mass .145 kg with an a baseball, mass .145 kg with an uncertainty in the speed of .100 m/suncertainty in the speed of .100 m/s

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What does the wave Function mean?What does the wave Function mean?

Nothing.Nothing. It is not possible to visually map it.It is not possible to visually map it. The square of the function is the The square of the function is the

probability of finding an electron near a probability of finding an electron near a particular spot.particular spot.

Best way to visualize it is by mapping Best way to visualize it is by mapping the places where the electron is likely to the places where the electron is likely to be found.be found.

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Pro

babi

lity

Distance from nucleus

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Sum

of

all P

roba

bili

ties

Sum

of

all P

roba

bili

ties

Distance from nucleusDistance from nucleus

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Defining the sizeDefining the size The nodal surface.The nodal surface. The size that encloses 90% to the The size that encloses 90% to the

total electron probability.total electron probability. NOT at a certain distance, but a most NOT at a certain distance, but a most

likely distance.likely distance. For the first solution it is a sphere. For the first solution it is a sphere.

We can construct atomic orbitals by drawing a boundary at the place where probability = 90%

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Note on online HW pp

#6 is correct - check your units!. When a question asks, “how much heat is

liberated,” your answer will be positive because there is no “negative” heat.

When a question asks, “what is the change in heat” then you have to indicate the change by a (+) or (-) sign.

When you use energy or heat in a mathematical equation (e.g., q = m∆TCp then you also have to show the sign.

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7.6 Quantum Numbers

There are many solutions to Schrödinger’s equation

Each solution can be described with 4 quantum numbers (n, l, m, s) that describe some aspect of the solution.

Analogous to y = mx + b describing a line (4 variables).

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Atomic Orbitals & Quantum Numbers

Principal Quantum Number (n) = the main energy level of the electron.

Tells us the size (distance from the nucleus) and energy of an orbital.

Has integer values of n = 1, 2, 3, . . .

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Angular Momentum Quantum Number (l)

Within each energy level the complex math of Schrodinger’s equation describes several shapes (l).

These shapes are called atomic orbitals

They are regions where there is a high probability of finding an electron.

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The 2nd quantum number Angular momentum quantum number l . Describes the shape of the orbital. Has integer values from 0 to n-1 l = 0 is called s and has shape of? l = 1 is called p l = 2 is called d l = 3 is called f l = 4 is called g

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3rd Quantum number (m)

Magnetic quantum number (m l)

Has integer values between -l and +l Tells orientation of each shape.

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S orbitals

+

n = 1n = 2

n = 3

1s

2s

3s

Orbitals are found in 3-D shells instead of 2-D Bohr orbits. The Bohr radius for n=1 was correct, however.

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P orbitals

+

n = 1n = 2

n = 3

“p” orbitals only exist in the 2nd shell and higher (n = 2, 3, ...)

3px 3py 3pz

2px 2py 2pz

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P Orbitals

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D orbitals

“d” orbitals only exist for n = 3, 4, 5….

+

n = 1n = 2

n = 3

3dz2 3dxz 3dyz 3dxy 3dx2-y2

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Three F orbitals

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Other four F orbitals

Do not appear until the 4th shell and higher

“The Shell Game” (n = 1)

+

n = 1n = 2

n = 3

“The Shell Game” n = 2

+

n = 1n = 2

n = 3

“The Shell Game” n = 3

+

n = 1n = 2

n = 3

• pppp

• pppp

• 99

Go to application, Atom in a BoxGo to application, Atom in a Box

pp

100

Quantum Numbers

n = # of sublevels per level

n2 = # of orbitals per level

Sublevel sets: 1 s, 3 p, 5 d, 7 f

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7.8 Electron Spin & the Pauli Principle

4th Quantum number (s) Electron spin quantum number (either

symbolized as “s” or as “ ms”) Can have 2 values only. Either +1/2 or -1/2 LD 1: 4.30 & 4.31 Electron Spin

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Figure 7.19Figure 7.19A Picture of A Picture of the Spinning the Spinning ElectronElectron

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Pauli Exclusion Principle No two electrons in the same atom can

have the same set of 4 quantum numbers. This means . . .

At most 2 electrons per orbital - each with different spins

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7.9 Polyelectronic Atoms7.9 Polyelectronic Atoms More than one electron.More than one electron. Three energy contributions.Three energy contributions. The The kinetickinetic energy of moving electrons. energy of moving electrons. The The potentialpotential energy of the energy of the attractionattraction

between the nucleus and the electrons.between the nucleus and the electrons. The The potentialpotential energy from energy from repulsionrepulsion of of

electrons.electrons.

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Polyelectronic atomsPolyelectronic atoms Can’t solve Schrödinger's equation exactly.Can’t solve Schrödinger's equation exactly. Difficulty is Difficulty is repulsionrepulsion of other electrons. of other electrons. Solution is to treat each electron as if it were Solution is to treat each electron as if it were

affected by the affected by the net fieldnet field of charge from the of charge from the attraction of the nucleus and the repulsion of attraction of the nucleus and the repulsion of the electrons.the electrons.

EffectiveEffective nuclear charge nuclear charge

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+11P

11 electrons

+11P 10 otherelectrons

e-Zeff

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Effective Nuclear charge Effective Nuclear charge Can be calculated fromCan be calculated from

E = -2.178 x 10E = -2.178 x 10-18-18 J (ZJ (Zeffeff22 / n / n22 ) )

andand

E = -2.178 x 10E = -2.178 x 10-18-18 J ZJ Zeffeff22 (1/ n (1/ nff

22 - 1/ n - 1/ nii22))

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Summary: Polyelectronic EffectSummary: Polyelectronic Effect In a hydrogen atom there is only one In a hydrogen atom there is only one

electron.electron. So, its energy So, its energy sublevelssublevels (orbitals) are (orbitals) are

equal (because no interference from equal (because no interference from other electrons).other electrons).

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Figure 7.18Figure 7.18Orbital Orbital Energy Energy Levels for Levels for the the Hydrogen Hydrogen Atom Atom (degenerate)(degenerate)

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Figure 7.18 Orbital Energy Levels for the H Atom (degenerate)Figure 7.18 Orbital Energy Levels for the H Atom (degenerate)

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Summary continuedSummary continued But, in a polyelectronic orbital the But, in a polyelectronic orbital the

sublevels are not equal in energy.sublevels are not equal in energy. Electrons “prefer” the order Electrons “prefer” the order s, p, d, fs, p, d, f.. E.g., E.g., the 2s electron “penetrates” to the the 2s electron “penetrates” to the

nucleus more than the 2p enucleus more than the 2p e--.. So, the 2s orbital is lower in energy.So, the 2s orbital is lower in energy. Penetration effects produces the Penetration effects produces the

Aufbau principle (arrow diagram) Aufbau principle (arrow diagram)

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Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

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7.10 The History of the Periodic Table7.10 The History of the Periodic Table Developed independently by German Developed independently by German

Julius Lothar Meyer and Russian Dmitri Julius Lothar Meyer and Russian Dmitri Mendeleev (1870”s).Mendeleev (1870”s).

Didn’t know much about the atom.Didn’t know much about the atom. Put in columns by similar properties.Put in columns by similar properties. Predicted properties of missing Predicted properties of missing

elements.elements.

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History of the Periodic Table Russian scientist, Dmitri Mendeleev,

taught chemistry in terms of properties. Mid 1800 - molar masses of elements

were known. He wrote down the elements in order of

increasing atomic mass. He found a pattern of repeating

properties.

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Mendeleev’s Table Grouped elements in columns by similar

properties in order of increasing atomic mass.

Found some inconsistencies - felt that the properties were more important than the mass, so switched order for some.

He found some gaps. He concluded . . . Must be undiscovered elements. Predicted their properties before they were

found. (Sc, Ga, Ge)

Mendeleev’s Early Periodic Table, Published in 1872

Note the spaces left for missing elements with atomic masses 44, 68, 72 and 100.

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Mendeleev’s Table Two questions remained: Why can most elements be arranged in

order of atomic mass, but a few can’t? What was the reason for chemical

periodicity? Mosely: found the patterns fit better

when arranged in order of nuclear charge (the atomic number vs. mass).

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The modern table The Periodic Law: physical & chemical

properties of the elements are periodic functions of their atomic numbers.

The Periodic Table: Arranges elements in order of increasing atomic number (not mass), so elements with similar properties are in the same group (column).

Let’s look at an example of this . . .

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Modern PT by atomic # (& properties) Compare Sb, Te, I (look at your PT)

Gp #

(Per. 5)15 16 17

Name Antimony Tellurium Iodine

Mass # 121.75 127.60 126.90

Symbol Sb Te IAtomic # 51 52 53

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The Modern Table Elements still grouped by properties. Similar properties in the same column. Order is in increasing atomic number. Added a column of elements Mendeleev

didn’t know about (noble gases). The noble gases weren’t found because

they didn’t react with anything. Last column on the Periodic Table Also added lanthanides & actinides.

122

7.11 The Aufbau Principle & the Periodic Table7.11 The Aufbau Principle & the Periodic Table

Aufbau is German for building up.Aufbau is German for building up. As the protons are added one by one, As the protons are added one by one,

the electrons fill up hydrogen-like the electrons fill up hydrogen-like orbitals.orbitals.

Fill up in order of energy levels.Fill up in order of energy levels. This causes difficulties because of the This causes difficulties because of the

overlap of orbitals of different energies.overlap of orbitals of different energies.

123

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

He with 2 electrons

124

Hund’s RuleHund’s Rule When electrons occupy orbitals of equal When electrons occupy orbitals of equal

energy they do energy they do notnot pair up until they pair up until they have to. (Each gets its own room)have to. (Each gets its own room)

Let’s determine the electron Let’s determine the electron configuration for configuration for PhosphorusPhosphorus

Need to account for 15 electrons (same Need to account for 15 electrons (same as atomic number)as atomic number)

125

The first two electrons go into the 1s orbital

Notice the opposite spins

only 13 more to go

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

126

The next electrons go into the 2s orbital

only 11 more

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

127

• The next electrons go into the 2p orbital

• only 5 more

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

128

• The next electrons go into the 3s orbital

• only 3 more

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

129

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

• The last three electrons go into the 3p orbitals.

• They each go into separate shapes

• 3 unpaired electrons

• 1s22s22p63s23p3

130

Orbital Diagrams Use individual orbitals Give subshell arrangement Each orbital takes one electron

before any other orbital in the same subshell can receive a second electron

131

Orbital Diagram for A Nitrogen Atom

N

1s 2s 2p 3s

132

Orbital Diagram for A Fluorine Atom

F

1s 2s 2p 3s

133

Orbital Diagram for A Magnesium Atom

Mg

1s 2s 2p 3s

134

Learning Check O1Write the orbital diagram for the electrons in an oxygen atom. . . Ans.

135

Solution O1Write the orbital diagram for the electrons in an oxygen atom.

1s 2s 2p 3s

136

Tr23 Aufbau PrincipleTr23 Aufbau Principle

What is the maximum electrons in each box?

Two

Which is a higher energy level, 4d or 5s?

4d

Which is farther from the nucleus, 4d or 5s?

5s

137

DetailsDetails Valence electronsValence electrons - s & p electrons in - s & p electrons in

the outermost energy sublevels (not d).the outermost energy sublevels (not d). Core electronsCore electrons- the inner electrons.- the inner electrons. Hund’s Rule Hund’s Rule - The lowest energy - The lowest energy

configuration for an atom is the one configuration for an atom is the one having the maximum number of having the maximum number of unpaired unpaired electrons in the orbitalelectrons in the orbital..

C 1sC 1s2 2 2s2s22 2p 2p22

138

Fill from the bottom up following Fill from the bottom up following the arrowsthe arrows

1s2s 2p3s 3p 3d4s 4p 4d 4f

5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f

• 1s2

• 2• electrons

2s2

• 4

2p6 3s2

• 12

3p6 4s2

• 20

3d10 4p6

5s2

• 38

4d10 5p6 6s2

• 56

139

DetailsDetails Elements in the Elements in the samesame column have the column have the

same outer same outer electron configurationelectron configuration.. Put in columns because of Put in columns because of similarsimilar

propertiesproperties.. Similar properties Similar properties becausebecause of electron of electron

configuration.configuration. Noble gases have Noble gases have filledfilled energy levels. energy levels. Transition metals are filling the Transition metals are filling the dd orbitals orbitals

140

Sublevel Blocks s1 s2 p1 p2 p3 p4 p5

p6

123 d1 - d10

456

f1 - f14

141

The “Extended” Periodic Table pp

142

1s1

1s22s1

1s22s22p63s1

1s22s22p63s23p64s1

1s22s22p63s23p64s23d104p65s1

1s22s22p63s23p64s23d104p65s24d10 5p66s1

1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p67s1

H1

Li3

Na11

K19

Rb37

Cs55

Fr87

143

He2

Ne10

Ar18

Kr36

Xe54

Rn86

1s2

1s22s22p6

1s22s22p63s23p6

1s22s22p63s23p64s23d104p6

1s22s22p63s23p64s23d104p65s24d105p6

1s22s22p63s23p64s23d104p65s24d10 5p66s24f145d106p6

144

ExceptionsExceptions Ti = [Ar] 4sTi = [Ar] 4s22 3d 3d22 V = [Ar] 4sV = [Ar] 4s22 3d 3d33

Cr = [Ar] 4sCr = [Ar] 4s11 3d 3d5 5

Mn = [Ar] 4sMn = [Ar] 4s22 3d 3d55

Half filled orbitals (only with d-orbitals).Half filled orbitals (only with d-orbitals). Scientists aren’t sure of why it happens.Scientists aren’t sure of why it happens. same for Cu [Ar] 4ssame for Cu [Ar] 4s11 3d 3d1010

145

Aufbau Web GraphicAufbau Web Graphic http://intro.chem.okstate.edu/Workshhttp://intro.chem.okstate.edu/Worksh

opFolder/Electronconfnew.htmlopFolder/Electronconfnew.html

146

More exceptionsMore exceptions

Lanthanum La: [Xe] 6sLanthanum La: [Xe] 6s22 5d 5d11 Cerium Ce: [Xe] 6sCerium Ce: [Xe] 6s22 4f 4f11 5d 5d11

Promethium Pr: [Xe] 6sPromethium Pr: [Xe] 6s22 4f 4f33 5d 5d00

Gadolinium Gd: [Xe] 6sGadolinium Gd: [Xe] 6s22 4f 4f77 5d 5d11

Lutetium Pr: [Xe] 6sLutetium Pr: [Xe] 6s22 4f 4f1414 5d 5d11

Then we go back to Aufbau filling:Then we go back to Aufbau filling: Hafnium Hf: [Xe] 6sHafnium Hf: [Xe] 6s22 4f 4f1414 5d 5d22

We’ll just pretend that all except Cu and We’ll just pretend that all except Cu and Cr follow the rules.Cr follow the rules.

147

A Quick DetourA Quick Detour The concept of shielding and The concept of shielding and

penetration of electrons in orbitals.penetration of electrons in orbitals. Catch the concepts, don’t worry too Catch the concepts, don’t worry too

much about the math.much about the math. Some AP questions.Some AP questions. This detour includes next 18 slides.This detour includes next 18 slides.

148

More PolyelectronicMore Polyelectronic We can use ZWe can use Zeffeff to to predict propertiespredict properties, if , if

we determine its pattern on the periodic we determine its pattern on the periodic table.table.

Can use the amount of energy it takes Can use the amount of energy it takes to to removeremove an electron for this. an electron for this.

Ionization Energy Ionization Energy - The energy - The energy necessary to remove an electron from a necessary to remove an electron from a gaseousgaseous atom. atom.

149

Remember this?Remember this? E = -2.18 x 10E = -2.18 x 10-18 -18 J(ZJ(Z22/n/n22)) was true for Bohr atom.was true for Bohr atom. Can be derived from quantum mechanical Can be derived from quantum mechanical

model as wellmodel as well For a mole of electrons being For a mole of electrons being removedremoved (so (so

use positive value for E). use positive value for E). E =(6.02 x 10E =(6.02 x 102323/mol)2.18 x 10/mol)2.18 x 10-18 -18 J(ZJ(Z22/n/n22)) E = 1.31 x 10E = 1.31 x 1066

J/mol(ZJ/mol(Z22/n/n22)) E = 1310 kJ/mol(ZE = 1310 kJ/mol(Z22/n/n22))

150

Example Example Calculate the ionization energy of BCalculate the ionization energy of B+4+4

E = 1310 kJ/mol(ZE = 1310 kJ/mol(Z22/n/n22)) 1310(51310(522)/1)/122 n= 1 because the n= 1 because the remainingremaining 1s e- is 1s e- is

being removed) = 32 750 kJ/molbeing removed) = 32 750 kJ/mol

151

Remember our simplified atomRemember our simplified atom

+11

11 e-

Zeff

1 e-

152

This gives usThis gives us Ionization energy = Ionization energy =

1310 kJ/mol(Z1310 kJ/mol(Zeffeff22/n/n22))

So we can measure ZSo we can measure Zeffeff

The ionization energy for a 1s electron The ionization energy for a 1s electron from sodium is 1.39 x 10from sodium is 1.39 x 1055 kJ/mol . kJ/mol .

The ionization energy for a 3s electron The ionization energy for a 3s electron from sodium is 4.95 x 10from sodium is 4.95 x 1022 kJ/mol . kJ/mol .

DemonstratesDemonstrates shielding.shielding.

153

Shielding The electron on the

outside energy level has to look through all the other energy levels to see the nucleus.

154

Shielding So, it is less affected by

the nucleus. So, lower effective

nuclear charge on it (blocking by the inner electrons)

And easier to be removed.

So, lower IE

155

ShieldingShielding Electrons on the Electrons on the higherhigher energy levels energy levels

tend to be tend to be farther outfarther out.. Have to look Have to look throughthrough the other electrons the other electrons

to see the nucleus.to see the nucleus. So, less affected by the nucleus.So, less affected by the nucleus. Lower Lower effectiveeffective nuclear charge nuclear charge on them on them

IfIf shielding were completely effective, Z shielding were completely effective, Zeffeff = 1 (= 1 (e.ge.g., in Na, 10 p., in Na, 10 p++ cancel 10 e cancel 10 e-- leaving the 11th pleaving the 11th p++ to have a Z effect on to have a Z effect on the 11th ethe 11th e--

Why isn’t the shielding complete?Why isn’t the shielding complete?

156

PenetrationPenetration There are levels to the electron There are levels to the electron

distribution for each orbital.distribution for each orbital.

2s

157

GraphicallyGraphically

Penetration

2s

Rad

ial P

roba

bili

ty

Distance from nucleus

158

GraphicallyGraphicallyR

adia

l Pro

babi

lity

Distance from nucleus

3s

159

Rad

ial P

roba

bili

ty

Distance from nucleus

3p

160

Rad

ial P

roba

bili

ty

Distance from nucleus

3d

161

Rad

ial P

roba

bili

ty

Distance from nucleus

4s

3d

162

Penetration effectPenetration effect The outer energy levels The outer energy levels penetratepenetrate the the

inner levels so the shielding of the inner levels so the shielding of the corecore electrons is not totally effective.electrons is not totally effective.

From most penetration to least From most penetration to least penetration the order ispenetration the order is

ns > np > nd > nf (within the ns > np > nd > nf (within the samesame energy level).energy level).

This is what gives us our order ofThis is what gives us our order of filling, filling, electrons prefer s and p. electrons prefer s and p.

163

How orbitals differHow orbitals differ The more positive the nucleus, the The more positive the nucleus, the

smaller the orbital.smaller the orbital. A sodium 1s orbital is the same A sodium 1s orbital is the same shapeshape

as a hydrogen 1s orbital, but it is as a hydrogen 1s orbital, but it is smallersmaller because the electron is more because the electron is more strongly attracted to the nucleus (11 Pstrongly attracted to the nucleus (11 P+ + vs. 1 Pvs. 1 P+ + ).).

The helium 1s is smaller than H’s 1s The helium 1s is smaller than H’s 1s also.also.

This provides for better shielding.This provides for better shielding.

164

Zef

f

1

2

4

5

1

165

Zef

f

1

2

4

5

1

If shielding is perfect Z= 1

166

Zef

f

1

2

4

5

1

No

shie

ldin

gZ

= Z ef

f

167

Zef

f

1

2

4

5

16

168

Back To Basics NowBack To Basics Now Let’s look at periodic trends.Let’s look at periodic trends.

169

7.12 Periodic Trends in Atomic Properties7.12 Periodic Trends in Atomic Properties

Ionization energy is the energy required to Ionization energy is the energy required to removeremove an electron from a an electron from a gaseousgaseous atom. atom.

XX(g)(g) + energy + energy X X++(g)(g) + e + e--

HighestHighest energy electron removed energy electron removed firstfirst. . First ionization energy (First ionization energy (II11) is that required ) is that required

to remove the first electron.to remove the first electron. Second ionization energy (Second ionization energy (II22) - the second ) - the second

electronelectron etc. etc.etc. etc.

170

Trends in ionization energyTrends in ionization energy for Mg for Mg

• II11 = 735 kJ/mole = 735 kJ/mole• II22 = 1445 kJ/mole = 1445 kJ/mole• II33 = 7730 kJ/mole = 7730 kJ/mole

The The effectiveeffective nuclear charge nuclear charge increasesincreases as as you remove electrons.you remove electrons.

Notice the big jump between INotice the big jump between I22 and I and I3.3.

It takes much more energy to remove a It takes much more energy to remove a corecore electron than a valence electron electron than a valence electron because there is because there is lessless shielding. shielding.

171

Symbol First Second ThirdHHeLiBeBCNO F Ne

1312 2731 520 900 800 1086 1402 1314 1681 2080

5247 7297 1757 2430 2352 2857 3391 3375 3963

11810 14840 3569 4619 4577 5301 6045 6276

172

Symbol First Second ThirdHHeLiBeBCNO F Ne

1312 2731 520 900 800 1086 1402 1314 1681 2080

5247 7297 1757 2430 2352 2857 3391 3375 3963

11810 14840 3569 4619 4577 5301 6045 6276

Why such Why such increase increase between the between the arrows?arrows?

Special Special stability of stability of noble gas noble gas configuration configuration makes it makes it harder to harder to remove an remove an inner shell inner shell electronelectron

173

Summary of Noble Gas Configuration effects on IE

174

Explain this trendExplain this trend For AlFor Al

• II11 = 580 kJ/mole = 580 kJ/mole

• II22 = 1815 kJ/mole = 1815 kJ/mole

• II33 = 2740 kJ/mole = 2740 kJ/mole

• II44 = 11,600 kJ/mole Answer . . . = 11,600 kJ/mole Answer . . .

II44 represents removing a core e- represents removing a core e-

175

Across a Across a PeriodPeriod & Down a Group & Down a Group Generally from left to right, Generally from left to right, II11 increases increases

because . . . because . . . There is a greater There is a greater nuclear chargenuclear charge with the with the

same same shieldingshielding.. As you go As you go downdown a a groupgroup II11 decreases decreases

because . . . because . . . Electrons are Electrons are fartherfarther away. away.

176

Sample FR ProblemSample FR Problem Given 3 different atomsGiven 3 different atoms

1s1s222s2s222p2p66 1s1s222s2s222p2p663s3s11 1s1s222s2s222p2p663s3s22

Which has Which has largestlargest I I11? . . .? . . . 1s1s222s2s222p2p66 (Ne) - found at (Ne) - found at right end of PTright end of PT; ;

also, also, 2p2p electrons electrons not effectivenot effective shielders shielders and the other two choices have and the other two choices have 3s3s electrons, which are effectively shielded by electrons, which are effectively shielded by the the corecore electrons electrons and fartherand farther from the from the nucleus.nucleus.

177

Sample FR ProblemSample FR Problem Given 3 different atomsGiven 3 different atoms

1s1s222s2s222p2p66 1s1s222s2s222p2p663s3s11 1s1s222s2s222p2p663s3s22

Which has Which has smallestsmallest I I22? . . .? . . . 1s1s222s2s222p2p663s3s22 (Mg) - both I (Mg) - both I11 & I & I22 involve involve

valence electrons (s electrons).valence electrons (s electrons). The Na The Na 1s1s222s2s222p2p663s3s11 would lose both a would lose both a

valence and a core electron from a p-valence and a core electron from a p-orbital (hard to do). orbital (hard to do).

The Ne The Ne 1s1s222s2s222p2p66 has ineffective shielding has ineffective shielding so its IE is relatively large.so its IE is relatively large.

178

It is not that simple, thoughIt is not that simple, though ZZeffeff changeschanges as you go across a period, as you go across a period,

so will so will II11.. Half filled and filled orbitals are harder Half filled and filled orbitals are harder

to remove electrons from.to remove electrons from. So those have higher ISo those have higher I11 energies. energies. Here’s what it looks like.Here’s what it looks like.

179

Firs

t Ion

izat

ion

ener

gy

Atomic number

He

He has a greater IE than H because . . .

same shielding (same level) but . . .

greater nuclear charge. Always ask yourself

about shielding and nuclear charge

H

180

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li has lower IE than H More shielding because . . . Further away This outweighs greater

nuclear charge

Li

181

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Be has higher IE than Li same shielding (same row) greater nuclear charge

(further away)

Li

Be

182

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He B has B has lowerlower IE than Be IE than Be same same shieldingshielding (row) (row) greater greater nuclear chargenuclear charge but but By removing an electron we By removing an electron we

make s orbital make s orbital filledfilled, which , which itself has lower energy so itself has lower energy so easier to remove and lower easier to remove and lower IE. IE. Li

Be

B

183

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

184

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

185

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

O

Oxygen breaks the pattern because removing an electron gets it down to 1/2-filled p sublevel (white board)

186

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

O

F

187

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

O

F

Ne Ne has a lower IE

than He. Why?. . . Both are full, but… Ne has more

shielding because Greater distance Always compare

shielding to distance.

188

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

O

F

Ne Na has a lower IE

than Li. Why? Both are s1 but Na has more

shielding because Greater distance

(4th level)Na

189

Firs

t Ion

izat

ion

ener

gy

Atomic number

190

Tr22A Summary of the previous trends

191

Figure 7.31Figure 7.31The Values of First Ionization Energy for the Elements in the First Six PeriodsThe Values of First Ionization Energy for the Elements in the First Six Periods

192

Figure 7.32Figure 7.32Trends in Ionization Energies for the Trends in Ionization Energies for the RepresentativeRepresentative Elements Elements

193

Electron Affinity The energy change associated with

adding an electron to a gaseous atom Opposite to IE (which is energy for losing

an electron. A + energy A+ + e-) Has negative value (since energy is lost) A + e- A- + energy Easiest to add e-s to group 17 (why?). Gets to full energy level (noble gas). LD 1: 5.32 Electron affinity of Chlorine

194

Electron Affinity Trends Period (row) Trends Increases from left to right because atoms get

smaller, with greater nuclear charge. Group (column) Trends Decreases as we go down a group (i.e.,

harder to add an e- (shielding from nucleus) Adding electrons to (-) ions Always more difficult to add another e- to an

already (-) charged ion, so these affinities have (+) values.

195

Electron Affinity Trends Adding electrons to negative ions Always more difficult to add another e- to an

already (-) charged ion, so these affinities have (+) values.

196

Table 5.17 p. 147Observe period and group trends

197

Atomic Size First problem: Where do you start

measuring. The electron cloud does not have a

definite edge. We get around this by measuring more

than 1 atom at a time as follows . . .

198

Atomic Size

Atomic Radius = half the distance between two nuclei of a diatomic molecule

LD 1:5.22 Radius of Chlorine.

}Radius

199

Trends in Atomic Size Influenced by two factors: Energy Level . . . Higher energy level is further away. Charge on the nucleus More charge pulls electrons in

closer. These are competing factors.

200

Periodic Trends Going across a period the radius gets

smaller because . . . Same energy level (same distance from

nucleus), but . . . More nuclear charge. So, outermost electrons are closer.

Na Mg Al Si P S Cl Ar

201

Group trends As we go down a

group Each atom has

another energy level

So the atoms get bigger (with some exceptions).

HLi

Na

K

Rb

Atomic Radii for Selected Atoms

Why is Ga smaller than Al?Gallium, unlike Al, is preceded by

10 d-block elementsThe expected increase in radius

caused by filling the 4th level is outweighed by a shrinking of electron cloud caused by Ga’s nuclear charge that is considerably larger (31 vs. 13) than for Al.

Compare Ga & Al on next slide (showing d-block)

Tr 26 Fig. 5.13 p. 141 Atomic Radii

Mg to Al size gets smaller because same level with more p+s

Zn to Ga size jumps because of electron shielding from the d-electrons that makes the increasing nuclear charge less effective, so the electron cloud gets larger.203

204

Overall

Atomic Number

Ato

mic

Rad

ius

(nm

)

H

Li

Ne

Ar

10

Na

K

Kr

Rb

205

Tr21A Fig 5.14 p 142 Atomic Radius vs Atomic Number

How does “effective” nuclear charge change left to rightIncreasesWhy is there a “peak” in Period 4?Inner 3d sublevel has filled & now in outer 4p sublevelWhy is there a U-shape curve across Period 5?

As add more 4d electrons, the shielding effect overcomes the effective nuclear charge.

206

Parts of the Periodic TableParts of the Periodic Table

207

The information it hidesThe information it hides Know the special groups.Know the special groups. It is the It is the numbernumber and and typetype of valence electrons of valence electrons

that determine an atom’s that determine an atom’s chemistrychemistry.. You can get the electron configuration from You can get the electron configuration from

the periodic table.the periodic table. Metals Metals loselose electrons and have the electrons and have the lowestlowest IE IE Nonmetals - Nonmetals - gaingain electrons and have the electrons and have the

most negativemost negative electron affinities. electron affinities.

208

The Properties of a Group: The Alkali MetalsThe Properties of a Group: The Alkali Metals

Doesn’t include hydrogen - behaves as Doesn’t include hydrogen - behaves as a nonmetal. Going down, get:a nonmetal. Going down, get:

Decrease in IEDecrease in IE increase in radiusincrease in radius Decrease in densityDecrease in density decrease in melting pointdecrease in melting point Behave as reducing agentsBehave as reducing agents

209

Reducing abilityReducing ability Lower IE = better reducing agents.Lower IE = better reducing agents. Cs > Rb > K > Na > Li in reducing abilityCs > Rb > K > Na > Li in reducing ability Works for Works for solidssolids, but , but notnot in aqueous in aqueous

solutions. Get opposite effect.solutions. Get opposite effect. In solution Li > K > NaIn solution Li > K > Na Why?Why? It’s the water - there is an energy It’s the water - there is an energy

change associated with dissolving.change associated with dissolving.

210

Hydration EnergyHydration Energy It is exothermicIt is exothermic

for Lifor Li++ = = -510 kJ/mol -510 kJ/mol

for Nafor Na+ + = = -402 kJ/mol-402 kJ/mol

for Kfor K++ = = -314 kJ/mol -314 kJ/mol Li’s is so big because it has a high charge Li’s is so big because it has a high charge

density; i.e., a lot of charge on a small atom.density; i.e., a lot of charge on a small atom. Li loses its electron more easily because of Li loses its electron more easily because of

this in aqueous solutionsthis in aqueous solutions

211

The reaction with waterThe reaction with water Na and K react explosively with water.Na and K react explosively with water. Li doesn’t. Li doesn’t. LD 1: 5.8, 5.10, 5.11, braniacsLD 1: 5.8, 5.10, 5.11, braniacs

Even though Li’s reaction has a more Even though Li’s reaction has a more negative negative H than that of Na and K.H than that of Na and K.

Na and K melt.Na and K melt. H does not tell you speed of reactionH does not tell you speed of reaction More about that in Chapter 12.More about that in Chapter 12.

212

Periodic (row) Trend Metals are at the left end. They let their electrons go easily So, have low electronegativity At the right end are the nonmetals. They want more electrons. Try to take them away from their

playmates. So, have high electronegativity.

213

Group (column) Trend The further down a group the farther the

electron is away and the more electrons an atom has (and more shielding).

More willing to share with another since the nucleus doesn’t hold on to the outer electrons so tightly (shielding).

So, low electronegativity.

214

Ionization energy, Electronegativity,

Electron affinity INCREASE

215

Ionization energy, ElectronegativityIonization energy, Electronegativity

Electron affinity INCREASEElectron affinity INCREASE

216

Atomic size increases, (shielding constant across a period)

Ionic size increases

217

Atomic size increases, (shielding Atomic size increases, (shielding constant across a period)constant across a period)

Ionic size increases

218

The Big Review Given 5 elements E:

2s22p5 G: 4d105s25p5 J: 2s22p2 L: 5d106s26p5 M: 2s22p4

ID block location (without PT). All are in p-block Which in same period? EJM same period (2nd) Same group? EGL same group (17)

219

The Big Review Given 5 elements E:

2s22p5 G: 4d105s25p5 J: 2s22p2 L: 5d106s26p5 M: 2s22p4

Which has highest e- affinity? E Forms 1- ion? EGL form 1 minus ions. Highest electronegativity? E (closest to upper right of PT)

220

The Big Review Given 5 elements

E: 2s22p5 G: 4d105s25p5 J: 2s22p2 L: 5d106s26p5 M: 2s22p4

Which is larger, G or G ion? G ion (-). Added electron, cloud is bigger Which contain(s) 7 valence e-? EGL (all have s2p5 outer electrons)