…and, in conclusion…
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Transcript of …and, in conclusion…
…and, in conclusion…
You will need to know the contributions of…
• Bohr
• Planck
• Einstein
• Heisenberg
• de Broglie
Q: How is light produced?
Q: How is light produced?
• A: An excited electron…
•
Q: How is light produced?
• A: An excited electron…
• loses energy…
•
Q: How is light produced?
• A: An excited electron…
• loses energy…
• as it falls…
Q: How is light produced?
• A: An excited electron…
• loses energy…
• as it falls…
• from a higher to a lower energy level,…
•
Q: How is light produced?
• A: An excited electron…
• loses energy…
• as it falls…
• from a higher to a lower energy level,…
• emitting that energy…
•
Q: How is light produced?
• A: An excited electron…
• loses energy…
• as it falls…
• from a higher to a lower energy level,…
• emitting that energy…
• as a photon of light
An electron that gains energy is excited:
moves to a higher energy level,
physically moves away from nucleus
An electron in its normal position is in its ground state
*
(gains energy)
Ground state
Excited *
• Light is produced*
As it loses energy
Ground state
Excited *
We use a * to mark an excited electron or atom.
• An atom can be excited by:
•
•
•
We use a * to mark an excited electron or atom.
• An atom can be excited by:
Heat (light bulbs, stars, sparks, flames)
Electricity (sparks, fluorescent bulbs) or
Chem. rxns (lightning bugs, glow sticks)
Let’s do the wave.
The wave equation
Where
c is the speed of light, 3.00 x 108 m/s
is the wavelength (the symbol, lambda, is the Greek “l” for length) and
is the frequency (the symbol, nu, is the Greek “n”)
c=
Please notice:
• Wavelength and frequency are inversely related.
• When wavelength increases, frequency decreases.
• Q: What is the frequency of light that has a wavelength of 570 nm(5.7x10-7m)?
• Q: What is the frequency of light that has a wavelength of 570 nm(5.7x10-7m)?
• c=
• Q: What is the frequency of light that has a wavelength of 570 nm(5.7x10-7m)?
• c==c/
• Q: What is the frequency of light that has a wavelength of 570 nm(5.7x10-7m)?
• c==c/=(3.00x108m/s) / (5.7x10-7m)
• Q: What is the frequency of light that has a wavelength of 570 nm(5.7x10-7m)?
• c==c/=(3.00x108m/s) / (5.7x10-7m)
• 5.3 x 1014 /s =5.3 x 1014 Hz
Next: Planck’s equation
• The energy of a photon is directly related to its frequency
E=h• where
• E is the energy (in Joules),
• is the frequency (in waves/s, or Hz), and
• h is the conversion factor, Planck’s constant.
h=6.63 x 10-34 Js
The electromagnetic spectrum
For any pair--
Which has greater , , E, v?
The electromagnetic spectrumIncreasing wavelength
Increasing frequency
Increasing energy
and, c is the velocity of light (c for constant!)
Visible light400 nm
700 nm
Short wavelength High energy High frequency
Long wavelength Low energy Low frequency
Fill in the missing information
Type of photon
c=
3x108m/s
(m) (s-1) E (per photon)
450 nm
93.3 MHz
353 m
9.47 x 10-21 J
4.03 x 10-19 J
Fill in the missing information
Type of photon
c=
3x108m/s
(m) (s-1) E (per photon)
3.00 x 108 m/s
450 nm 6.67 x 1014 Hz
4.42 x 10-19 J
93.3 MHz
353 m
9.47 x 10-21 J
4.03 x 10-19 J
Fill in the missing information
Type of photon
c=
3x108m/s
(m) (s-1) E (per photon)
3.00 x 108 m/s
450 nm 6.67 x 1014 Hz
4.42 x 10-19 J
3.00 x 108 m/s
3.22 m 93.3 MHz 6.19 x 10-26 J
353 m
9.47 x 10-21 J
4.03 x 10-19 J
Fill in the missing information
Type of photon
c=
3x108m/s
(m) (s-1) E (per photon)
3.00 x 108 m/s
450 nm 6.67 x 1014 Hz
4.42 x 10-19 J
3.00 x 108 m/s
3.22 m 93.3 MHz 6.19 x 10-26 J
3.00 x 108 m/s
353 m 8.50 x 105 Hz
5.63 x 10-28 J
9.47 x 10-21 J
4.03 x 10-19 J
Fill in the missing information
Type of photon
c=
3x108m/s
(m) (s-1) E (per photon)
3.00 x 108 m/s
450 nm 6.67 x 1014 Hz
4.42 x 10-19 J
3.00 x 108 m/s
3.22 m 93.3 MHz 6.19 x 10-26 J
3.00 x 108 m/s
353 m 8.50 x 105 Hz
5.63 x 10-28 J
3.00 x 108 m/s
2.10 x 10-5 m
1.43 x 1013 Hz
9.47 x 10-21 J
4.03 x 10-19 J
Fill in the missing information
Type of photon
c=
3x108m/s
(m) (s-1) E (per photon)
3.00 x 108 m/s
450 nm 6.67 x 1014 Hz
4.42 x 10-19 J
3.00 x 108 m/s
3.22 m 93.3 MHz 6.19 x 10-26 J
3.00 x 108 m/s
353 m 8.50 x 105 Hz
5.63 x 10-28 J
3.00 x 108 m/s
2.10 x 10-5 m
1.43 x 1013 Hz
9.47 x 10-21 J
3.00 x 108 m/s
4.94 x 10-7 m
6.08 x 1014 Hz
4.03 x 10-19 J
Fill in the missing information
Type of photon
c=
3x108m/s
(m) (s-1) E (per photon)
Blue or indigo light
3.00 x 108 m/s
450 nm 6.67 x 1014 Hz
4.42 x 10-19 J
FM radio 3.00 x 108 m/s
3.22 m 93.3 MHz 6.19 x 10-26 J
AM radio 3.00 x 108 m/s
353 m 8.50 x 105 Hz
5.63 x 10-28 J
IR 3.00 x 108 m/s
2.10 x 10-5 m
1.43 x 1013 Hz
9.47 x 10-21 J
Blue or Green light
3.00 x 108 m/s
4.94 x 10-7 m
6.08 x 1014 Hz
4.03 x 10-19 J
The Bohr Model of the atom• Bohr’s solar system model
-- shows why the H gives off only 4 wavelengths of visible light.
• He calculated the energy that the electrons did give off, and the differences in energy.
Bohr drew a picture like this
Electron loses energy
Electron gains energy
• These 4. No more. There is nothing between the levels– no “half-transitions”
Visible wavelengths produced by
hydrogen atoms
In the hydrogen spectrum
• The wavelengths are:– 410 nm (violet)– 434 nm (blue)– 486 nm (green)– 656 nm (red)
4.85x10-19J
4.58x10-19J
4.09x10-19 J
3.03x10-19J
In the hydrogen spectrum
4.85x10-19J
4.58x10-19J
4.09x10-19 J
3.03x10-19J
In the hydrogen spectrum
What is the energy difference between these two levels?
4.85x10-19J
4.58x10-19J
4.09x10-19 J
3.03x10-19J
In the hydrogen spectrum
What is the energy difference between these two levels?
.49 x 10-19 J
• These energies represent the differences in the energy levels…
…and that’s how we know where the energy levels are.
Other phenomena that teach us about electrons and light
The photoelectric effect
– Described by Einstein for his Nobel prize– Light knocks electrons off a metal– Indicates the particle nature of
light
One photon excites one electron
Other phenomena that teach us about electrons and light
• Heisenberg’s Uncertainty Principle
– “You cannot determine both the location and momentum of a particle exactly.”
– If you measure one, you change the other unpredictably
– Leads to the wave and particle natures of everything
Gratuitous joke
Heisenberg was pulled over on the highway. The officer asks,
“Do you know how fast you were going?”
Heisenberg replies,
Gratuitous joke
Heisenberg was pulled over on the highway. The officer asks,
“Do you know how fast you were going?”
Heisenberg replies,
“No, but I do know where I am!”
Other phenomena that teach us about electrons and light
• DeBroglie’s wavelength
– Describes the wave nature of particles– Considers the uncertainty in position as a
wavelength
Electron Configurations
…and now, the rest of the story
Fe (2,8,14,2)
• --An electron configuration (EC) shows the location of all electrons in an atom or ion.
• --In an atom, number of electrons = number of protons = atomic number
• --Electrons are found around the nucleus of an atom in specific energy levels.
Levels have sublevels!
Levels have sublevels!
Sublevels have orbitals!
1st energy level
• -has one sublevel, 1s
• -An s sublevel (spherical) has one orbital,
• -An orbital can hold two electronsZ
XY
• So the electron configuration of hydrogen and helium are more properly written
• 1H 1s1
• 2He 1s2
• 1H 1s1
• 2He 1s2
• The 1 refers to the energy level
• 1H 1s1
• 2He 1s2
• The s refers to the sublevel
• 1H 1s1
• 2He 1s2
• The superscripts are the number of electrons in this sublevel.
2nd energy level
• -has 2s (bigger, still spherical) and 2p (has 3 bi-lobed orbitals in x, y, and z directions)
• -holds up to 8 electrons total
(2 in the s and 3 x 2 in the p)
Z
XY
Z
XY
Z
XY
• 3Li 1s22s1
• 4Be 1s22s2
• 5B 1s22s22p1
• 6C 1s22s22p2
• 7N 1s22s22p3 …
Third energy level
has three sublevels, 3s, 3p, and 3d.
The 3s and 3p sublevels are similar in structure (but bigger) than the s and p sublevels seen before.
The 3d sublevel
• (and any d) has five orbitals of varying shapes.
• These orbitals can hold two electrons each for a total of ten electrons.
• The 3d sublevel is the highest energy sublevel of energy level 3, so high, in fact, that energy level 4 begins to fill (the 4s sublevel fills) before the 3d sublevel
See text
Z
XY
Z
XY
Z
XY
Z
XY
Z
XY
See handout
The fourth energy level has four sublevels (notice the trend?) They are called 4s, 4p, 4d, and 4f. The s, p, and d sublevels are structured as before.
See handout
The f sublevel has seven orbitals, and can hold up to fourteen electrons.
The 5s sublevel is filled before the 4d, and the 5p and 6s sublevels precede the 4f.
Let’s look at a picture instead
You must remember this…
• s=1 orbital, 2 electrons
• p=3 orbitals, 6 electrons
• d=5 orbitals, 10 electrons
• f=7 orbitals, 14 electrons
The Aufbau diagram
This structure is shown below. Boxes are orbitals, each can hold two electrons
1s
2s
3s
4s
5s
6s
7s
7p
6p
5p
4p
3p
2p
3d
4d
5d
6d 5f
4f
1s
2s
3s
4s
5s
6s
7s
7p
6p
5p
4p
3p
2p
3d
4d
5d
6d 5f
4f
Rules, rules, rules.
• Orbitals are filled according to three rules:– Aufbau (building up) principle—lower energy
sublevels are filled first– Pauli exclusion principle—electrons sharing
an orbital must have opposite spins– Hund’s Rule—when a sublevel has several
orbitals, electrons will distribute to separate orbitals with parallel spins, before sharing orbitals with opposite spins
1s
2s
3s
4s
5s
6s
7s
7p
6p
5p
4p
3p
2p
3d
4d
5d
6d 5f
4f
Levels have sublevels
• All Electron configurations are some subset of the order shown below. Only the last sublevel might be incomplete
• 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10
5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d10 7p6…
Watch out for two things
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d10 7p6 … gets old.
Ex:
87Fr 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s1
87Fr [Rn] 7s1
(Radon is a noble gas, and accounts for the first 86 electrons)
Look for the last octet and use a noble gas core
• Practice:
• Write the full EC for Titanium (element 22) and write the EC with a noble gas core
• Practice:
• Write the full EC for Titanium (element 22) and write the EC with a noble gas core
• A) Ti 1s2 2s2 2p6 3s2 3p6 4s2 3d2
• and Ti [Ar] 4s2 3d2
…and watch out for Cu and Cr!• Chromium, copper and a few others
rearrange electrons to become more stable.
• Sublevel energies go down when a sublevel is full or half full.
• Cr 1s2 2s2 2p6 3s2 3p6 4s2 3d4 becomes• Cr 1s2 2s2 2p6 3s2 3p6 4s1 3d5 and
• Cu 1s2 2s2 2p6 3s2 3p6 4s2 3d9 becomes• Cu 1s2 2s2 2p6 3s2 3p6 4s1 3d10
Problems:
1. Write the electron configurations for phosphorus and molybdenum. Then draw the aufbau diagrams for these elements.
2. Write the complete electron configurations for magnesium, sulfur, and potassium. Then write their electron configurations using the symbols for the noble gases.
3. What element is represented by [Ne]3s23p6?
4. Determine the electron configuration for the last SUBLEVEL of the following elements: S, Pt, Sr, K, and Al.
5. The an unknown element has an electron configuration of 1s22s22p63s23p4.
A. What is the element?
B. What does the superscript 6 refer to?
C. What does the letter s refer to?
D. What does the coefficient 3 refer to?
6. Write the electron configuration for calcium, a nutrient essential to healthy bone growth and development.
7. Write the electron configuration for copper, which is used in pennies.
8. Use the symbols for the noble gases to write the electron configurations for the following elements:
A. Zr B. U C. Rn
9. Write the electron configuration and draw the orbital diagrams for the following elements:
A. Carbon B. Silver C. Aluminum
VOCABULARY
• Electron configuration• Atomic number• Energy level• Valence level• Sublevel• s,p,d,f• Orbital• Spin
• Proton• Electron• Spherical• Two-lobed• Dumbell-shaped• Aufbau principle• Pauli’s exclusion
principle• Hund’s rule
Be able to:
• Describe the levels, sublevels, and orbitals.• Recreate the aufbau order from the periodic
chart• Write a complete EC and EC with a noble gas
core for any element• Determine the last sublevel, and number of
electrons there from a position on a periodic chart
• Identify a position on the chart and the element from an EC
• Fill out an aufbau diagram for any element
Trends in the Periodic Chart
…since the position on the chart indicates electrons, and electrons are responsible for physical and chemical
properties…
• …the position on the periodic chart indicates the physical and chemical properties of elements!
• Opposite charges attract– electrons are attracted by the protons in the nucleus
Simple
• Valence electrons
– The representative (tall) columns represent the number of valence electrons
– Transition elements have only two valence electrons, but have a part-filled d sublevel
Simple
• Ionization pattern
• Metals
- have only a few valence electrons
-lose these electrons, empty their valence level
-form positive ions
Simple
• Ionization pattern
• Non-metals have
-more valence electrons
-gain electrons to fill valence level
-form negative ions
Medium
• Atomic size
• In a column, a lower row indicates an extra energy level
• Outer energy levels are larger
• The largest atom in a column is the bottom element
Medium
• Ionization energy —the energy required to remove an electron
X + IE X+ + e-
• Outer energy levels are farther from the nucleus• It is easier to remove an electron from a larger
energy level• The lowest ionization energy is at the bottom of the
column
Medium
• Electronegativity —the attraction an atom has for a shared pair of electrons
• See IE—the highest electronegativity is at the top
Medium
• Electron affinity —attraction an atom has for an electron from the outside
X + e- X- + EA
• See e-neg—the highest electron affinity is at the top
One moment…
As you go across a row, you get more protons in the nucleus
• They attract the electrons better
• Each energy level gets smaller
Hard
• Atoms get smaller as you go across a row
• Ionization energy gets larger
• Electronegativity gets larger
• Electron affinity gets larger
--All because there are more protons--
Recap
• Atomic size
• INCREASES as you go down
and left
Recap
• Electronegativity, ionization energy, and electron affinity
• INCREASE as you go up
and right
Pop Quiz
• Which element on the entire periodic chart is the largest?
• Smallest?
• Which element on the entire periodic chart has the largest IE?
• Smallest?
Pop Quiz
• Which element on the entire periodic chart has the largest e-negativity?
• Smallest?
• Which element on the entire periodic chart has the largest EA?
• Smallest?
Pop Quiz
• Who’s your favorite pop star?
• Which has the greatest / least: Size, IE, EA, e-neg?
C
Sn I
F
The diagonal effect
• Of the previous four elements, the ones in the same row and column are easy, right?
• What can you say about carbon and iodine?
• They might be just about the same!
The metal/nonmetal line
Diagonal effect!
(due to electronegativity or EA)
Hard (cont’d)
• Ionic radius
Negative ions are (way!) larger than their atom
Positive ions are (way!) smaller than their atom
• Which has the largest / smallest ion?
Li
K Ca
Be
• Which has the largest / smallest ion?
S
Te I
Cl
• Which has the smallest / largest ion?
Mg
Sr Te
S
• Which has the smallest / largest ion?
+2 -2
+2 -2
Mg
Sr Te
S
Hard (cont’d)
• Second and third ionizations
• If you ionize an atom, you make a (+) ion
• It’s harder to ionize it again
• It gets way harder after you empty the valence level
Hard (cont’d)
• First, second, and third ionization energies
X + IEX+1 + e-
X+1 + IE2X+2 + e-
X+2 + IE3X+3 + e-
Shielding
• Shielding –weakening of attraction due to electrons interfering with attraction of the nucleus
• Shielding increases a little as you go across a period (not as much as attraction)
• Shielding jumps tremendously as you start a new energy level
Remem-mem-mem…
• Ionic radius
Negative ions are (way!) larger than their atom
Positive ions are (way!) smaller than their atom
Remem-mem-mem…
• Ionic radius
Negative ions are (way!) larger than their atom
…due to shielding by the extra electrons
Positive ions are (way!) smaller than their atom
…because they have lost shielding or shielded electrons
Disclaimer
• Noble gasses have no electronegativity—they don’t share electrons
• Noble gasses have no electron affinity—they don’t gain electrons
• Most metals have no electron affinity—they don’t gain electrons
• Ionization Energies in kJ/mol• 1 2 3 4 5H 1312He 23725250Li 520 7297 11810Be 899 1757 14845 21000B 800 2426 3659 25020 32820C 1086 2352 4619 6221 37820N 1402 2855 4576 7473 9442O 1314 3388 5296 7467 10987F 1680 3375 6045 8408 11020Ne 2080 3963 6130 9361 12180Na 496 4563 6913 9541 13350Mg 737 1450 7731 10545 13627
• Ionization Energies in kJ/mol• 1 2 3 4 5H 1312He 23725250Li 520 7297 11810Be 899 1757 14845 21000B 800 2426 3659 25020 32820C 1086 2352 4619 6221 37820N 1402 2855 4576 7473 9442O 1314 3388 5296 7467 10987F 1680 3375 6045 8408 11020Ne 2080 3963 6130 9361 12180Na 496 4563 6913 9541 13350Mg 737 1450 7731 10545 13627
Size of metal atoms
Size of Atoms (radius, nm)
Size of Anions
A positive charge is
worth about three energy
levels!
Size of Cations
Electron Affinity*, Electronegativity*, Ionization energy
Size
Atomic number, shielding, diagonal effect
Th-th-that’s all, folks.