October 5th, 2015
Electron Configurations: Chapter 5 sections 5.2
& 5.3
• What is the atomic mass of hafnium if, out
of every 100 atoms, 5 have mass 176, 19
have mass 177, 27 have mass 178, 14 have
mass 179, and 35 have mass 180.0?
Why should I care?
The number of
electrons
surrounding the
nucleus determines
all the chemical
properties.
Electron Configuration: Shows
the most stable arrangement of
electrons around the nucleus.
Energy Level
1
1s
# of
Sublevel electrons
“S” Sublevel = Sphere Shaped
1 orbital
Holds two (2) electrons
“P” Sublevel = Dumbbell Shaped
Three (3) orbitals
Holds two (2) electrons in each
orbital (6 electrons total)
“D” Sublevel = Shaped like a cloverleaf
Five (5) orbitals
Holds two (2) electrons in each
orbital (10 electrons total)
“F” Sublevel = Balloon Shaped
Seven (7) orbitals
Holds two (2) electrons in each
orbital (14 electrons total)
Sublevel
Orbitals
Electrons
s
1
2
p
3
6
d
5
10
f
7
14
Electron Configuration
H=
1
1s
Orbital Filling Diagram
H = __
1s
ATOMIC NUMBER
Pauli Exclusion Principle:
2 electrons in an orbital must have
opposite spin
Electron Configuration
He =
2
1s
Orbital Filling Diagram
He = __
1s
Can Hold:
1st Energy Level
s
2nd Energy Level
s p
3rd Energy Level
s p d
4th Energy Level
s p d f
5th Energy Level
s p d f
6th Energy Level
s p d f
Electron Configuration
Li =
2
1
1s 2s
Orbital Filling Diagram
Li = __ __
1s
2s
Aufbau Principle: Electrons
are stable in the lowest
energy level possible
Aufbau comes from the German word
aufbauprinzip which means building up.
Electron Configuration
Be=
2
2
1s 2s
Orbital Filling Diagram
Be= __
1s
__
2s
Electron Configuration
B=
2
2
1
1s 2s 2p
Orbital Filling Diagram
B = __ __
1s
__ __ __
2s
2p
Hund’s Rule: One electron
enters each orbital until all
have one of same spin, then
pairs will be added.
Electron Configuration
C=
2
2
2
1s 2s 2p
Orbital Filling Diagram
C = __ __
1s
__ __ __
2s
2p
Electron Configuration
N=
2
2
3
1s 2s 2p
Orbital Filling Diagram
N = __ __
1s
__ __ __
2s
2p
Electron Configuration
O=
2
2
4
1s 2s 2p
Orbital Filling Diagram
O = __ __
1s
__ __ __
2s
2p
Electron Configuration
F=
2
2
5
1s 2s 2p
Orbital Filling Diagram
F = __ __
1s
__ __ __
2s
2p
Electron Configuration
Ne =
2
2
6
1s 2s 2p
Orbital Filling Diagram
Ne = __ __
1s
__ __ __
2s
2p
Rule of Eight:
An atom is most stable when
it has 8 electrons in its outer
shell, called an Octet
1
2
3
4
5
6
7
1
2
3
4
5
6
7
__ __ __ __ __
3d
1
2
3
4
5
6
7
__
__
__
__
4f
__
__
__
Assignment
• Complete Electron Configurations &
Orbital Diagram practice (WS)
• Finish atomic history (WS)
• Book Readings are due Friday.