3-Atomic Structure

1
3-Atomic Structure

• Overview
• Characteristics of Atoms
• Interaction b/tw matter and light
• Photoelectric Effect
• Absorption and Emission Spectra
• Electron behavior
• Quantum numbers

2
Atomic Structure

• Atomic orbitals
• Orbital energies
• Electron configuration and the periodic table
• Periodic table
• Periodic properties
• Energy

3
Characteristics of Atoms

• Atoms possess mass
• Atoms contain positive nuclei
• Atoms contain electrons
• Atoms occupy volume
• Atoms have various properties
• Atoms attract one another
• Atoms can combine with one another to form
  molecules

4
Atomic Structure

• Atomic structure studied through atomic
  interaction with light
• Light electromagnetic radiation
• carries energy through space
• moves at 3.00 x 108 m/s in vacuum
• wavelike characteristics

5
Electromagnetic Spectrum
6
Visible Spectrum
7
Wavelength (?) Frequency (?)
amplitude
? number of complete cycles to pass given point
in 1 second
8
Energy

• c ? x ? 3.00 x 108 m/s
• long wavelength ? low frequency

Low Energy
High Energy
short wavelength ? high frequency
9
Energy

• Mathematical relationship
• E h?
• E energy
• h Plancks constant 6.63 x 1034 J s
• ? frequency in s1

10
Energy

• Mathematical relationship
• E h?
• c ? x ?

Energy directly proportional to
frequency inversely proportional to wavelength
11
Problems 3-1, 2, 3

• a) Calculate the wavelength of light with a
  frequency ? 5.77 x 1014 s1
• b) What is the energy of this light?
• 2. Which is higher in energy, light of
  wave-length of 250 nm or light of 5.4 x 107 m?
• 3. a) What is the frequency of light with an
  energy of 3.4 x 1019 J?
• b) What is the wavelength of light with an
  energy of 1.4 x 1020 J?

12
Photoelectric Effect

• Light on metal surface
• Electrons emitted
• Threshold frequency, ?o
• If ? lt ?o, no photoelectric effect
• If ? gt ?o, photoelectric effect
• As ? ?, kinetic energy of electrons ?

13
Photoelectric Effect

• Einstein energy ? frequency
• If ? lt ?o electron doesnt have enough energy to
  leave the atom
• If ? gt ?o electron does have enough energy to
  leave the atom
• Energy is transferred from light to electron,
  extra is kinetic energy of electron
• Ephoton h?photon h?o KEelectron
• KEelectron h?photon h?o
• Animation

14
Problem 3-4

• A given metal has a photoelectric threshold
  frequency of ?o 1.3 x 1014 s?1. If light of ?
  455 nm is used to produce the photoelectric
  effect, determine the kinetic energy of the
  electrons that are produced.

15
Bohr Model

• Line spectra
• Light through a prism ? continuous spectrum

Ordinary white light
16
Bohr Model

• Line spectra
• Light from gas-discharge tube
• through a prism ? line spectrum

H2 discharge tube
17
Line Spectra (emission)

• White light

H
He
Ne
18
Line Spectra (absorption)
Gas-filled tube
Light source
19
Bohr Model

• For hydrogen

C 3.29 x 1015 s1
Niels Bohr Electron energy in the atom is
quantized.
n 1, 2, 3,. RH 2.18 x 1018 J
20
Bohr Model

• ?Eatom ?Eelectron h?
• ?E Ef Ei h?

Minus sign free electron has zero energy
Line spectrum Photoelectric effect
21
Bohr Energy Levels
22
Electrons

• All electrons have same charge and mass
• Electrons have properties of waves and particles
  (De Broglie)

23
Heisenberg Uncertainty Principle

• Cannot simultaneously know the position and
  momentum of electron
• ???x h
• Recognition that classical mechanics dont work
  at atomic level.

24
Schrödinger Equation

• Erwin Schrödinger 1926
• Wave functions with discrete energies
• Less empirical, more theoretical
• ?n En
• ?n wave functions or orbitals
• ?n2 probability density functions

25
Quantum Numbers

• Each orbital defined by 3 quantum numbers
• Quantum number number that labels state of
  electron and specifies the value of a property

26
Quantum Numbers

• Principal quantum number, n (shell)
• Specifies energy of electron (analogous to Bohrs
  n)
• Average distance from nucleus
• n 1, 2, 3, 4..

27
Quantum Numbers

• Azimuthal quantum number, ? (subshell)
• 0, 1, 2 n1
• n 1, ? 0
• n 2, ? 0 or 1
• n 3, ? 0, 1, or 2
• Etc.

0 1 2 3 4
s p d f g
28
Quantum Numbers

• Magnetic quantum number, m?
• Describes the orientation of orbital in space
• m? ?. ?
• If ? 2, m? 2, 1, 0, 1, 2

29
Problem 3-5

• Fill in the quantum numbers in the table below.

n ? m?
3 0 0 3s
2 2, 1, 0, 1, 2
0
2p
30
Schrödinger Equation

• Wave equations ?
• Each electron has ? E associated w/ it
• Probability Density Functions ?2
• -graphical depiction of high probability of
  finding electron

31
Probability Density Functions
Link to Ron Rineharts page

• ? energy
• ?2 probability density function
• s, p, d, f, g
• 1s

3s
2s
Node area of 0 electron density
32
Probability Density Functions

• 2p

Node area of 0 electron density
nodes
Link to Ron Rineharts page
33
Electrons and Orbitals

• Pauli Exclusion Principle no two electrons in
  the same atom may have the same quantum numbers
• Electron spin quantum number ms ?½
• Electrons are spin paired within a given orbital

34
Electrons and Orbitals

• n 1
• ? 0, m? 0, ms ?½
• 2 electrons possible
• 1,0,0,½ and 1,0,0,½
• 2 electrons per orbital
• 1s1 H
• 1s2 He

35
Electrons and Orbitals

• n 2
• ? 0, m? 0, ms ?½
• 2,0,0, ?½
• 2 electrons possible
• n 2
• ? 1, m? 1,0,1, ms ?½
• 2,1,1, ?½ 2,1,0, ?½ 2,1,1, ?½
• 6 electrons possible

36
Electron Configurations

• n 1
• 1s 2 electrons possible
• H 1e 1s1

?
He 2e 1s2
??
37
Electron Configurations

• n 2
• 2s 2 electrons possible

Li 3e 1s2 2s1
?
2s
??
1s
Be 4e 1s2 2s2
??
2s
??
1s
38
Electron Configurations

• n 2
• 2p ? 1, m? 1, 0, 1
• 3 x 2p orbitals (px, py, pz) 6 electrons possible

B 5e 1s2 2s2 2p1
39
Electron Configurations

• n 2
• 2p ? 1, m? 1, 0, 1
• 3 x 2p orbitals (px, py, pz) 6 electrons possible

2p
?
B 5e 1s2 2s2 2p1
??
2s
1s
??
40
Electron Configurations

• n 2
• 2p ? 1, m? 1, 0, 1

C 6e 1s2 2s2 2p2
Hunds Rule for degenerate orbitals, the lowest
energy is attained when electrons w/ same spin is
maximized
41
Problem 3-6

• Write electron configurations and depict the
  electrons for N, O, F, and Ne.

42
Electron Configurations

• n 3
• 3s, 3p, 3d

Na 11e 1s2 2s2 2p63s1
43
Electron Configurations

• n 3
• 3s, 3p, 3d

Mg 12e 1s2 2s2 2p63s2
44
Electron Configurations

• n 3
• 3s, 3p, 3d

Al 13e 1s2 2s2 2p63s23p1
45
Electron Configurations

• n 3
• 3s, 3p, 3d

Si 14e 1s2 2s2 2p63s23p2
46
Electron Configurations

• n 3
• 3s, 3p, 3d

P 15e 1s2 2s2 2p63s23p3
47
Electron Configurations

• n 3
• 3s, 3p, 3d

S 16e 1s2 2s2 2p63s23p4
48
Electron Configurations

• n 3
• 3s, 3p, 3d

Cl 17e 1s2 2s2 2p63s23p5
49
Electron Configurations

• n 3
• 3s, 3p, 3d

Ar 18e 1s2 2s2 2p63s23p6
50
Electron Configurations

• 3d vs. 4s
• Filling order

1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 5g 6s 6p
6d 7s 7p
51
Electron Configurations
4p
3d
K
?
4s
3p
??
??
??
??
3s
2p
??
??
??
??
2s
1s
??
52
Electron Configurations
4p
3d
Ca
??
4s
3p
??
??
??
??
3s
2p
??
??
??
??
2s
1s
??
53
Electron Configurations
4p
?
3d
Sc
??
4s
3p
??
??
??
??
3s
2p
??
??
??
??
2s
1s
??
54
Electron Configurations
4p
?
?
3d
Ti
??
4s
3p
??
??
??
??
3s
2p
??
??
??
??
2s
Link to OSU site
1s
??
55
Problem 3-7

• Write the electron configurations for the
  transition metals V Zn. Fill in the
  corresponding boxes to denote the electronic spin.