Electron Configurations

1
Electron Configurations
2
New Model of the Atom

• 1926 further refined Bohrs model of the atom
  by developing the quantum mechanical model

3
Comparison to Bohrs Model
Electrons in levels Level Max e- 1 2
2 8 3 18 P and n0 in
nucleus
Gives probability of finding an electron in an
area Levels are broken into sublevels
Defines exact location of electron
4
Electron Configurations

• Electron configuration the arrangement of
  electrons in levels and sublevels
• There are 4 sublevels s p d and f.
• Each sublevel can be further broken down into
  orbitals that each hold 2 electrons.

5
Electron Configuration Rules

• There are 3 rules that explain how electrons
  occupy levels, sublevels, and orbitals.
• Aufbau principle
• Pauli exclusion principle
• Hunds rule

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Aufbau Principle

• An electron occupies the lowest-energy sublevel
  that can receive it.

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How to Remember Order
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How to Use Periodic Table

• Start at top left of periodic table.
• Work your way left to right.
• As you finish a row, move down.
• Remember the d sublevels number is one behind
  the period.
• Remember the f sublevels number is two behind
  the period.
• 4f follows 6s and 5f follows 7s.

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How to Use Periodic Table, continued

• Write the level and sublevel filled followed by a
  superscript to indicate the number of electrons
  in that sublevel.
• s holds maximum of 2
• p holds maximum of 6
• d holds maximum of 10
• f holds maximum of 14

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Electron Configurations

• 3d7

Number of electrons in the sublevel
Energy Level
Sublevel
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2
4f14 etc.
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OVERLAPSWhy are d and f orbitals always in lower
energy levels?

• d and f orbitals require LARGE amounts of energy
  to create.
• According to the Aufbau principle we must skip a
  sublevel that requires a large amount of energy
  (d and f orbtials) for one in a higher level but
  lower energy
• FOLLOW THE PERIODIC TABLE IN ORDER!

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Lets Try It!

• Write the electron configuration for the
  following elements
• H
• Li
• N
• Ne
• K
• Zn
• Pb

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Lets Try It!

• Write the electron configuration for the
  following elements
• H 1s1
• Li 1s2 2s1
• N 1s2 2s2 2p3
• Ne 1s2 2s2 2p6
• K 1s2 2s2 2p6 3s2 3p6 4s1
• Zn 1s2 2s2 2p6 3s2 3p6 4s2 3d10
• Pb 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6
  6s2 4f14 5d10 6p2

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YOU TRY THESE!

• Write the electron configuration for the
  following elements
• He
• Mg
• O
• P
• S
• Fe
• Ag

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YOU TRY THESE! Answers

• Write the electron configuration for the
  following elements
• He 1s2
• Mg 1s2 2s2 2p6 3s2
• O 1s2 2s2 2p4
• P 1s2 2s2 2p6 3s2 3p3
• S 1s2 2s2 2p6 3s2 3p4
• Fe 1s2 2s2 2p6 3s2 3p6 4s2 3d6
• Ag 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d9

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Noble Gas Notation

• A way of abbreviating long electron
  configurations
• Since we are only concerned about the outermost
  electrons, we can skip to places we know are
  completely full (noble gases), and then finish
  the configuration

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Noble Gas Notation

• Step 1 Find the closest noble gas to the atom,
  WITHOUT GOING OVER the number of electrons in the
  atom. Write the noble gas in brackets .
• Step 2 Find where to resume by finding the next
  energy level (row in periodic table).
• Step 3 Resume the configuration starting with
  ns2 where n is the next level

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Noble Gas Notation

• Chlorine
• Longhand is 1s2 2s2 2p6 3s2 3p5
• You can abbreviate the first 10 electrons with a
  noble gas, Neon. Ne replaces 1s2 2s2 2p6
• The next energy level after Neon is 3
• So you start at level 3 on the periodic table and
  continue with 3s and 3p until you arrive at
  chlorine.
• Ne 3s2 3p5

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Practice Noble Gas Notation

• Write the noble gas notation for each of the
  following atoms
• Cl
• K
• Ca
• I
• Bi

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Practice Noble Gas Notation

• Write the noble gas notation for each of the
  following atoms
• Cl Ne3s2 3p5
• K Ar4s1
• Ca Ar4s2
• I Kr5s2 4d10 5p5
• Bi Xe6s2 4f14 5d10 6p3

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You Try These

• Write the noble gas notation for each of the
  following atoms.
• He
• Mg
• O
• P
• S
• Fe
• Ag

22
You Try These

• Write the noble gas notation for each of the
  following atoms.
• He 1s2
• Mg Ne 3s2
• O He 2s2 2p4
• P Ne 3s2 3p3
• S Ne 3s2 3p4
• Fe Ar 4s2 3d6
• Ag Kr 5s2 4d9