Electron Configuration

1
Electron Configuration

• Building the Atom

2
Remember Atomic Number (Z) the number of
protons in the nucleus of the atom. Mass Number
(A) the number of protons and neutrons in the
nucleus of the atom. Neutron Number (N) A - Z
N
3

• LOCATION OF ELECTRONS IN THE ATOM
• Electron Cloud
• Energy Levels
• Sublevels
• Orbitals

4

• LOCATION OF ELECTRONS IN THE ATOM
• Sublevels have (degenerate states) that
• we call orbitals.
• These sublevels are named s, p, d, f, g, etc.
• The energy level determines the number
• of sublevels...

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LOCATION OF ELECTRONS IN THE ATOM
Sublevels s- one orbital p- three orbitals d-
five orbitals f- seven orbitals Etc...
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LOCATION OF ELECTRONS IN THE ATOM
It turns out, in each orbital, there can be a
maximum of two electrons. So... s- 2 electrons
total p- 6 electrons total d- 10 electrons
total f- 14 electrons total
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Orbital diagrams and electron configurations
Orbital diagrams help show how the electrons are
distributed within the sublevels.
NOTICE THAT WHEN ELECTRONS PAIR THEY HAVE
OPPOSITE SPINS.
1s
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PAULI EXCLUSION PRINCIPLE...
No two electrons can have the same quantum
numbers or no more than two electrons can be
found in any given orbital.
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HUNDS RULE the most stable arrangement of
electrons is that with the maximum number of
unpaired electrons, all with the same spin
direction. In other wordselectrons dont pair
until they have too!
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Orbital Diagrams
Mg
What element is this????
3s
2px
2py
2pz
2s
1s
etc...
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• Another way to write this is by using electron
  configuration notation

Mg
1s22s22p63s2
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ORDER OF CHOICE
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p,
6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p...
Why? Energy of some orbitals overlap higher
orbitals. Page 97
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• Lets practice
• Assignment
• Electron Configuration Level One and Two
• Electron Configuration Wkst

end day 1
14
Orbital diagrams and electron configurations
Orbital diagrams help show how the electrons are
distributed within the sublevels.
NOTICE THAT WHEN ELECTRONS PAIR THEY HAVE
OPPOSITE SPINS.
1s
remember...?
15
Orbital Diagrams
Mg
What element is this????
3s
2px
2py
2pz
2s
1s
etc...
remember...?
16

• Another way to write this is by using electron
  configuration notation

Mg
1s22s22p63s2
remember...?
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• Another way to write this is by using noble gas
  notation

Mg
Ne3s2
Since Ne has a configuration of 1s22s22p6
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Lets practice Valence Electron Configuration
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Connections Do you see any relationship between
the electron configuration and where the
element is located on the Periodic Table?
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• You should be able to
• Write the electron configuration
• Draw the orbital diagram
• Write the noble gas notation
• And predict the element

Let's do it!
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• Assignment
• Electron Configuration Wkst 2

end day 2