1. Wave Description of Light
Electromagnetic radiation is a form of energy that exhibits wavelike behavior as it travels through space
Wavelength (λ)
Distance between corresponding points on adjacent waves.
Unit: nm,cm,m
Frequency (ν)
Number of waves that pass a specific point in a given time
Unit: Hz or waves/sec
Recall that Speed = Distance/time (m/sec)
Speed of light (c)
C = λ ν
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2. Behavior of Light Photoelectric effect Quantum
The emission of electrons when light shines on the metal
Scientists found that below a certain frequency, no electrons were emitted.
Light also behaves as a particle: Since hot objects do not emit em energy continuously, they must emit energy in small chunks called quanta.
Quantum
Minimum quantity of energy that can be gained or lost by an atom
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3. Light as a particle and a wave Planck and Einstein
Max Planck: Relationship between quantum of energy and wave frequency
Planck’s constant h = x J-s
E = hν E is energy, ν is frequency
Albert Einstein: Established dual wave-particle nature of light 1st
Einstein explained PE effect by proposing that EM radiation is absorbed by matter only in whole numbers of photons.
Electron is knocked off metal surface only if struck by one photon with certain minimum energy.
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4. Louis de Broglie Louis de Broglie answered this. His equation:
Because we know that light has a particle nature, we might ask if matter has wave nature.
Louis de Broglie answered this. His equation:
λ = h/mv
Lambda is a wave property.
Momentum (mass x velocity) is a particle property.
In one equation, de Broglie summarized the concepts of waves and particles as they apply to high-speed, low mass objects.
Results of de Broglie’s discovery include X-ray diffraction and electron microscopy techniques used to study small objects.
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5. Quantum Theory Ground state: An atom’s lowest energy state
Excited state: Higher potential energy than ground state.
Photon: A particle of electromagnetic radiation having zero mass and carrying a quantum of energy (i.e., packet of light)
Only certain wavelengths of light are emitted by hydrogen atoms when electric current is passed through—Why?
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6. Niels Bohr links hydrogen’s electron with photon emission
Bohr proposed that an electron circles the nucleus in allowed orbits at specific energy levels.
Lowest energy is close to nucleus
Bohr’s theory explained the spectral lines seen in hydrogen’s line emission spectrum, but it did not hold true for other elements.
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7. Arrangement of Electrons in Atoms
Principles of electromagnetic radiation led to Bohr’s model of the atom.
Electron location is described using identification numbers called quantum numbers.
Rules for expressing electron location results in a unique electron configuration for each element.
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8. Building electron configurations for the ground state of an atom
Aufbau: Lowest energy level 1st
Pauli Exclusion: Only 2 e- per orbital, opposite spin
Hund: One electron per orbital until that level is full (same spin) 1s 3s 2s 4s 3p 2p 4p 3d
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9. Mullis

10. p6 s1 s2 p1 p2 p3 p4 p5 d1 d2 d3 d4 d5 d6 d7 d8 d9 f1 f2 f3 f4 f5 f6Sc 4 4d Y 5 5d La 6 6d Ac f1 f2 f3 f4 f5 f6 f7 f8 f9
f10
f11
f12
f13
f14 4f 5f

11. Quantum Numbers Principal quantum number, n
Angular momentum quantum number, l
Magnetic quantum number, ml
Spin quantum number, ms
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12. Azimuthal quantum number = Angular momentum quantum number
Depends on the value of n
Values of l starts at 0 and increases to n-1
This number defines the shape of the orbital.
Orbital l
s 0
p 1
d 2
f 3
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13. Magnetic quantum number
Magnetic quantum number is the orientation of an orbital around the nucleus.
It is the number of orbitals in a sublevel.
The s sublevel has 1 orbital.
The p sublevel has 3 orbitals.
The d sublevel has 5 orbitals.
The f sublevel has 7 orbitals.
Orbitals per sublevel
s 1
p 3
d 5
f 7
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14. Magnetic quantum number, ml
Gives the 3d orientation of each orbital.
Has value from –l to + l
Example:
3p refers to orbitals with n = 3 and l = 1.
Values of ml = -1,0,1
These three numbers correspond the 3 possible orientations of the dumbbell-shaped p orbitals (x,y and z axis).
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15. Quantum numbers 1s ____ 2s ____ 2p ____ ____ ____ 3s _____
Magnetic quantum number
Principal quantum number
Angular momentum quantum number
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16. Quantum numbers 1s ____ 2s ____ 2p ____ ____ ____ 3s _____
ms = -1/2
ms = +1/2
ml =0
ml = -1
ml = +1
Magnetic quantum number
Principal quantum number
Angular momentum quantum number
[ for a p orbital, l = 1]
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