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Electrons

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Title: Electrons

1
Electrons Atoms
2
Quantum Mechanical Model

Electrons probabilities vs. points of matter
The probability of finding an electron within a
space can be represented by a fuzzy cloud. These
shapes are where we believe the electrons will
live 90 of the time.

3
ENERGY LEVELS

The model designates energy levels of electrons
by principal quantum numbers. Each quantum
number refers to a major or principal energy
level in the atom (n1,2,3,4..)

4
ENERGY SUBLEVELS

Within each principal energy level, the electrons
occupy energy sublevels. (They are not ORBITS
because the electron is not confined to a fixed
circular path.)
Because electrons within the sublevels occupy
specific cloud-shaped regions, the cloud shapes
are called atomic orbitals. The atomic orbitals
are denoted by letters (s, p, d, f, . . . .)

5
QM Electron Structure
6
Key Things to Remember

At most, only 2 electrons exist in any single
orbital.
An orbital within a higher energy level is
larger than the same type of orbital for a lower
energy level (i.e. the 3s orbital is larger than
the 2s orbital which is larger than the 1s
orbital).
Electrons in higher energy levels are, on
average, further from the nucleus.
The principal quantum number (energy level)
sublevels within that principal energy level.

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9
d Orbitals
http//www.uky.edu/holler/html/orbitals_2.html
10
f Orbitals
http//www.uky.edu/holler/html/orbitals_2.html
11
d and f orbitals more difficult to visualize

Link to site with simulation of various orbital
shapes University of Kentucky
Link to the Orbitron Gallery. University of
Sheffield

12
Electron Energy and Orbitals

In general, electrons in orbitals for higher
levels have more energy.
Orbital energy by type f gt d gt p gt s
However, as the atom gets larger ( of electrons
increases), there is some overlap between
orbitals and principle energy levels.

13
Electron Configurations

The way in which electrons are arranged around
the nuclei of atoms are called electron
configurations. Three rules tell you how to find
the configurations of electrons

14
Electron Configuration Rules

Aufbau principle Electrons enter orbitals of
lowest energy first.
Pauli exclusion principle An atomic orbital may
describe at most two electrons. To occupy the
same orbital, the two electrons must have
opposite spins. (shown as arrows)
Hunds rule When electrons occupy orbitals of
equal energy, one electron enters each orbital
until all the orbitals contain one electron with
parallel spins. Second electrons then add to
each orbital so that their spins are opposite
those of the first electrons.

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16
Aufbau Diagrams useful when remembering the
order in which orbitals fill
17
Valence Electrons

The ones we most care about
Largely determine the chemical nature of the atom
(what is it likely to react with)
They are the electrons in the highest principle
energy (quantum) level only.
Other electrons do have an impact to chemical
character of the atom just not as much

18
EXAMPLE 1 Determine the electron configuration
of silicon (Si), atomic 14

Answer 1s22s22p63s23p2
Alternatively He 2s22p63s23p2
Alternatively Ne 3s23p2
Valence Electrons 4 in the 3rd principle
energy level

19
EXAMPLE 2 Determine the electron configuration
of calcium (Ca), atomic 20

Answer 1s22s22p63s23p64s2
Alternatively Ar 4s2

20
EXAMPLE 3 Determine the electron configuration
of silver (Ag), atomic 47

Answer 1s22s22p63s23p64s23d104p65s24d9
Alternatively Kr 5s24d9

21
Periodic Table vs. ConfigurationsLast electron
filling . . .
http//www.uky.edu/holler/html/orbitals_2.html
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23
Aufbau Exceptions Cr Cu

For Chromium
Aufbau 1s22s22p63s23p63d44s2
Actual 1s22s22p63s23p63d54s1
One 4s electron goes to 3d to half fill 3d
sub-level
For Copper
Aufbau 1s22s22p63s23p63d94s2
Actual 1s22s22p63s23p63d104s1
One 4s electron goes to 3d to complete 3d
sub-level
In these cases, completely filled sub-level has
less energy than a half-filled, which has less
energy than a full s orbital and less than
half-filled d sub-level.

24
Electron Configurations and the Periodic table
25
The Row (or Period)

The row (or period) number that the element
occupies is the same as the highest principle
quantum level, n, occupied by the highest
electrons.

Periods Are arranged horizontally across the
periodic table (rows 1-7)
Example Aluminum has its highest energy
electrons in the 3rd principle quantum level.
Aluminum is in the 3rd row or period

Al 1s2 2s2 2p6 3s2 3p1
Al
6th Period
27
Sections or Blocks

Certain sections or blocks of the periodic table
correspond to the energy sublevels occupied by
the highest energy electrons.

28
Example Al has its highest energy electrons in
a p sublevel. Al is in the p section with other
atoms with their highest energy e- also in a p
sublevel.
H 1s1
He 1s2
F 2p5

Be 2s2
B 2p1
C 2p2
N 2p3
Ne 2p6
Li 2s1
O 2p4
Na 3s1
Mg 3s2
Cl 3p5
Al 3p1
Si 3p2
P 3p3
S 3p4
Ar 3p6
K 4s1
Ca 4s2
Zn 3d10
As 4p3
Be 4p5
Sc 3d1
Ti 3d2
V 3d3
Cr 4s13d5
Mn 3d5
Fe 3d6
Co 3d7
Ga 4p1
Ge 4p2
Se 4p4
Kr 4p6
Ni 3d8
Cu 4s13d10
Sr 5s2
Rb 5s1
Nb 4d3
Mo 5s14d5
Ru 4d6
Rh 4d7
Sn 5p2
I 5p5
Xe 5p6
Cd 4d10
Zr 4d2
Tc 4d5
In 5p1
Sb 5p3
Te 5p4
Y 4d1
Ni 4d8
Ag 5s14d10
Cs 6s1
Hf 5d2
Ta 5d3
W 6s15d5
Re 5d5
Os 5d6
Ir 5d7
At 6p5
Rn 6p6
La 5d1
Ni 5d8
Ba 6s2
Tl 6p1
Pb 6p2
Bi 6p3
Po 6p4
Hg 5d10
Au 6s15d10
Mt 6d7
Fr 7s1
Bh 6d5
Hs 6d6
Ra 7s2
Rf 6d2
Db 6d3
Sg 7s16d5
Ac 6d1
29
Groups

The number of columns or groups in a sublevel
block is the same as the total number of
electrons that can occupy that sublevel

30
Example There are 6 columns in the p block of
elements. A p sublevel can contain 6 total
electrons
columns
6
1
2
3
4
5
H 1s1
He 1s2
F 2p5

The column an element occupies in a sublevel
block is the same as the number of electrons in
that sublevel.

32
Example Al is in the first column of the p
block on the periodic table. Al has one
electron in the 3p sublevel.
H 1s1
He 1s2
F 2p5

Be 2s2
B 2p1
C 2p2
N 2p3
Ne 2p6
Li 2s1
O 2p4
Na 3s1
Mg 3s2
Cl 3p5
Si 3p2
P 3p3
S 3p4
Ar 3p6
K 4s1
Ca 4s2
Zn 3d10
As 4p3
Be 4p5
Sc 3d1
Ti 3d2
V 3d3
Cr 4s13d5
Mn 3d5
Fe 3d6
Co 3d7
Ga 4p1
Ge 4p2
Se 4p4
Kr 4p6
Ni 3d8
Cu 4s13d10
Sr 5s2
Rb 5s1
Nb 4d3
Mo 5s14d5
Ru 4d6
Rh 4d7
Sn 5p2
I 5p5
Xe 5p6
Cd 4d10
Zr 4d2
Tc 4d5
In 5p1
Sb 5p3
Te 5p4
Y 4d1
Ni 4d8
Ag 5s14d10
Cs 6s1
Hf 5d2
Ta 5d3
W 6s15d5
Re 5d5
Os 5d6
Ir 5d7
At 6p5
Rn 6p6
La 5d1
Ni 5d8
Ba 6s2
Tl 6p1
Pb 6p2
Bi 6p3
Po 6p4
Hg 5d10
Au 6s15d10
Mt 6d7
Fr 7s1
Bh 6d5
Hs 6d6
Ra 7s2
Rf 6d2
Db 6d3
Sg 7s16d5
Ac 6d1
33
Relationships

These relationships mean that we can read the
electron configuration for Aluminum directly from
the periodic table.

34
Example Aluminum is in the 3rd row, the p
block, and the first column of that block. So
Als highest energy electron is 3p1 electron
1
H 1s1
He 1s2
F 2p5