The Electronic Structure of Atoms

1
The Electronic Structure of Atoms
Chapter 4
2
Properties of Waves
Wavelength (l) is the distance between identical
points on successive waves.
Amplitude is the vertical distance from the
midline of a wave to the peak or trough.
7.1
3
Properties of Waves
Frequency (n) is the number of waves that pass
through a particular point in 1 second (Hz 1
cycle/s).
The speed (u) of the wave l x n
7.1
4
7.1
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l x n c
l c/n
l 3.00 x 108 m/s / 6.0 x 104 Hz
l 5.0 x 103 m
l 5.0 x 1012 nm
7.1
6
Mystery, Photoelectric EffectSolved by
Einstein in 1905
hn

• Light has both
• wave nature
• particle nature

KE e-
Photon is a particle of light
7.2
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7.3
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7.3
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Bohrs Model of the Atom (1913)

1. e- can only have specific (quantized) energy
   values
2. light is emitted as e- moves from one energy
   level to a lower energy level

7.3
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7.3
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Chemistry in Action Element from the Sun
In 1868, Pierre Janssen detected a new dark line
in the solar emission spectrum that did not match
known emission lines
Mystery element was named Helium
In 1895, William Ramsey discovered helium in a
mineral of uranium (from alpha decay).
12
Chemistry in Action Laser The Splendid Light
Laser light is (1) intense, (2) monoenergetic,
and (3) coherent
13
Chemistry in Action Electron Microscopy
le 0.004 nm
STM image of iron atoms on copper surface
14
Schrodinger Wave Equation

• In 1926 Schrodinger wrote an equation that
  described both the particle and wave nature of
  the e-
• Wave function (Y) describes
• . energy of e- with a given Y
• . probability of finding e- in a volume of space
• Schrodingers equation can only be solved exactly
  for the hydrogen atom. Must approximate its
  solution for multi-electron systems.

7.5
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Order of orbitals (filling) in multi-electron atom
1s lt 2s lt 2p lt 3s lt 3p lt 4s lt 3d lt 4p lt 5s lt 4d lt
5p lt 6s
7.7
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Fill up electrons in lowest energy orbitals
(Aufbau principle)
Li 3 electrons
Be 4 electrons
B 5 electrons
C 6 electrons
Li 1s22s1
Be 1s22s2
B 1s22s22p1
H 1 electron
He 2 electrons
H 1s1
He 1s2
7.7
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C 6 electrons
N 7 electrons
O 8 electrons
F 9 electrons
Ne 10 electrons
C 1s22s22p2
N 1s22s22p3
O 1s22s22p4
F 1s22s22p5
Ne 1s22s22p6
7.7
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Electron configuration is how the electrons are
distributed among the various atomic orbitals in
an atom.
1s1
Orbital diagram
H
7.8
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Mg 12 electrons
1s lt 2s lt 2p lt 3s lt 3p lt 4s
1s22s22p63s2
2 2 6 2 12 electrons
Abbreviated as Ne3s2
Ne 1s22s22p6
Cl 17 electrons
1s lt 2s lt 2p lt 3s lt 3p lt 4s
1s22s22p63s23p5
2 2 6 2 5 17 electrons
Last electron added to 3p orbital
n 3
l 1
ml -1, 0, or 1
ms ½ or -½
7.8
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Outermost subshell being filled with electrons
7.8
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7.8