So 3.0 x 108 m/sec = 7.00 x 109 m ( = 3.0 x 108 m/sec = 4 ...ν = 3.0 x 108 m/sec = 4.3 x 1016 1/sec...
Transcript of So 3.0 x 108 m/sec = 7.00 x 109 m ( = 3.0 x 108 m/sec = 4 ...ν = 3.0 x 108 m/sec = 4.3 x 1016 1/sec...
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Chapter 11 Modern Atomic Theory Notes
Electromagnetic radiation energy that travels through space as waves.Waves have three primary characteristics:
Wavelength ( lambda) distance between two consecutive peaks or troughs in a wave. Unit = meter
Frequency ( nu) indicates how many waves pass a given point per second. Unit = Hertz (Hz)
Speed velocity (c = speed of light = 3.0 x 108 m/sec) indicates how fast a given peak moves in a unit of time
ex: If red light was a wavelength of 7.00 x 109 m ,what is its frequency?
So 3.0 x 108 m/sec = 7.00 x 109 m (ν)
ν = 3.0 x 108 m/sec = 4.3 x 1016 1/sec or 4.3 x 10 16 Hz 7.00 x 10 9 m
c = λν
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Electromagnetic radiation (light) is divided into various classes according to wavelength.
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Wave Particle Theory Light as waves Light as photons"In 1905 Einstein ... suggested that light itself could behave like little particles
or quanta, with energy proportional to the frequency (the colour) of the light. These particles of light are what we now call photons. Einstein's suggestion went straight to the heart of Quantum Theory, and began to expose the fundamental conceptual difficulties associated with it. Indeed it was for this work that he was awarded the Nobel prize in 1921." http://www.tcd.ie/Physics/Schools/what/atoms/quantum/duality.html
Photon/quantum packet of energy a “particle” of electromagnetic radiation
Excited State atom with excess energyWhen a Photon/light wave hits an electron its transfers energy to that electron and thus the electron is moved to a higher energy level.Ground State lowest possible energy state When an electron releases that extra energy it also emits a photon/light wave.• Wavelengths of light carry different amounts of energy per photon• Only certain types of photons are produced (see only certain colors)• Quantized only certain energy levels (and therefore colors) are allowed
Bohr Model suggested that electrons move around the nucleus in circular orbitsIncorrect but usefull for discribing excited and ground states.
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The electrons on this Bohr model atom have been hit by photons and are currently in an Excited State. In order to release the excess energy they must give off a photon of distinct light which corresponds to how far the electron drops. After giving off this energy the atom will be back in its Ground State .
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We can only see the changes between an Excited State and the Ground State. However, this occurs throughout the entire electronmagnetic spectrum and these changes in energy levels have been studied for every atom known today. An atom always gives off the same pattern of light.
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Wave Mechanical Model (Quantum Mechanical Model)The Bohr model is severely lacking in desribing many of the atom to atom interactions which have been observed through experimentation. To account for these observations a mathematical model was created by a large team of scientists and it is called the Wave Mechanical Model (WMM). The WMM divides and subdivides the areas electrons can be found into Energy Levels, then Sublevels, and finally Orbitals.
The description of an electron within an Orbital is said to be 95% accurate allowing for some transitions between orbitals as energy is exchanged. This also takes into account the Heisenberg Uncertainty Principle that states it is impossible to know both the location and velocity of an object. The more you know about where an electron occupies a certain point in space the less you know about how it moves and the converse is also true. Principle Energy Level (n) Largest area which is divided up into smaller areas.
The energy levels are designated by numbers 17.They are also called principle quantum numbers
Sublevel (l) The largest subdivision within each principle energy levelThe electron in a given sublevel have the same energyIf electrons are in different sublevels then the energy is slightly differentlowest energy sublevel is s, then p, then d, and then f is the most energy
Orbital The further subdivision of the sublevels where 2 electrons can be foundThe s sublevel contains 1 orbitalThe p sublevel contains 3 orbitalsThe d sublevel contains 5 orbitalsThe f sublevel contains 7 orbitals ** No more than two electrons can occupy an orbital**an orbital can be empty, halffilled, filled
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Summary
Principle # of # of orbitals present Total # of Maximum # of Energy Level sublevels s p d f orbitals electrons
1 1 1s 1 2
2 2 2s 2p 2p 2p 4 8
3 3 3s 3p 3p 3p 3d 3d 3d 3d 3d 9 18
4 4 4s 4p 4p 4p 4d 4d 4d 4d 4d 16 324f 4f 4f 4f 4f 4f 4f
Orginally it was believed that electrons always filled up orbitals starting with the lowest energy level and proceeded up higher and higher energy levels until all the electrons in the atom would occupy an orbital. However, this was adjusted drastically after Aufbau suggested a new order.
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1s22s2 2p63s2 3p6 3d104s2 4p6 4d10 4f145s2 5p6 5d10 5f146s2 6p6 6d10 7s2 7p6
Order of Electrons for Hydrogen does not work for all of the elements, which led us to Aufbau's Order.
1. Start Here
2. Then follow this diagonal
3. And so on
4. And so on
5. Until
6. all the
7. electrons
8. have orbitals
1 2 3 4
5 6 7
With HydrogenStart Here
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Shapes of orbitals All s orbitals are spherical as the principle energy level increases the diameter increases. All p orbitals are dumbbell shaped all have the same size and shape within an energy level
Each additional energy level of electrons is farther from the nucleus with more room between orbitals at the higher energy levels which leads to the introduction of the d and f orbitals.
n = 1 s orbital in the middle
n = 2 s and p orbitalssecond layer
n = 3 s, p and d(not drawn)third layer
I know the drawing isn't that good and that my skill is limited. You will not be required to draw, I just want you to understand what the s, p, d, and f's represent when we write them out.
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Orbital Diagram describes the placement of electrons in orbitals use arrows to represent electrons with spin line represents orbital
________ full ________ halffull ________ empty
Hund’s Rule All orbitals within a sublevel must contain at least one electron before any orbital can have two
Electron Configuration arrangement of the electrons among the various orbitals of the atom
Aufbau Order Tool to predict the order in which sublevels will fill (On the back of your periodic table.)
Ar has 18 electrons 1s2 2s2 2p6 3s2 3p6 the superscripts 2+2+6+ 2+6 = 18 electrons
K has 19 electrons 1s 2 2s2 2p6 3s2 3p6 4s1 the superscripts 2+2+6+ 2+6+1 = 19 electrons
Fe has 26 electrons 1s 2 2s2 2p6 3s2 3p6 4s2 3d6 the superscripts 2+2+6+ 2+6+2+6 = 26 electrons
Electron Spin motion that resembles earth rotating on its axis clockwise or counterclockwise
Represented by arrows point up and down.
Pauli Exclusion Principle two electrons in the same orbitals must have opposite spins
_________ _________ _________1s2 correct orientation 1s2 no possible 1s2 not possible
K has 19 electrons 1s2 2s2 2p6 3s2 3p6 4s1
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Noble Gas Configuration Shorthand configuration that substitutes a noble gas for electrons
Lets look at our previous 3 examples. Ar is a Noble Gas and its configuration is the same as K and Fe up to the last couple of orbitals. We can write [Ar] to represent that part of the electron configuration.
Ar has 18 electrons 1s2 2s2 2p6 3s2 3p6
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Periodic Table
Dimitri Mendeleev1869 developed the first version of the periodic table.He expressed the regularities as a periodic function of the atomic mass.
Henry Moseley revised Mendeleev’s periodic table by describing regularities in physical and chemical properties as periodic functions of the atomic number
Groups (family) vertical column Periods horizontal rowsElements with similiar valence electrons configurations Period number corresponds to the principal Group 1 alkali metals reactive quantum number of valence electronsGroup 2 alkaline earth metals reactiveGroup 312 transition metalsGroup 15 nitrogen familyGroup 16 oxygen family reactiveGroup 17 halogens very reactiveGroup 18 noble gases
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Metallic Character Increases down a group Decreases across a period
Ionization Energy energy required to remove an electron from an individual atom in a gas phase M(g) > M+(g) + e• Metals lose electrons to nonmetals so relatively low energy is needed• High ionization energy means an electron is hard to remove
Decreases down a group Increases across a period
Atomic Size Increases down a group Decreases across a period
Ionic Size depends upon how many electrons the atom has lost or gained.Cation Ca+2/Ca Ca larger because Ca +2 lost 2 electronsAnion S2/S S2 larger because S2 gained 2 electrons
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Attachments
h2linespectrum.mov
orbitalenergies.mov
SMART Notebook
SMART Notebook
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