1s 2s 2p 3s 3p 3d

n = 1

n = 2n = 3

NUCLEUS

1s

2s 2p

3s

3p 3d

4s 4p 4d 4f

Energy Level

Sublevels Total Orbitals

1 s 1s

2 s,p 1s+3p = 4

3 s,p,d 1s+3p+5d = 9

4 s,p,d,f 1s+3p+5d+7f = 16

n n types n2

The Electron Configuration

• Explain the pattern of configuration using the Periodic Table.

• Explain the Aufbau, Pauli and Hund rules.

• Write the electron configuration or orbital box diagrams for a variety of atoms and ions.

Pauli Exclusion Principle

Electrons are constantly spinning which results in a magnetic field. Two electrons can occupy the same orbital only if they have opposite spins.

Each orientation for a sublevel contains a maximum of 2 e-.

Energy Level

Sublevels Total # e- capacity

1 s 1 2

2 s,p 1+3 = 4 8

3 s,p,d 1+3+5 = 9 18

4 s,p,d,f 1+3+5+7 = 16 32

n n types n2 2n2

1s 2s 2p 3s 3p 3d

n = 1

n = 2n = 3

Aufbau Principle

Unexcited electrons fill the lowest, most stable, energy orbital available – ground state.

Range of energies contains some overlap between higher principle levels.

Hund ruleElectrons must enter empty orbitals of equal energy first before joining occupied orbitals.

Electron Configuration

Orbital Box Diagrams

1s 2s 2p 3s 3p 3d4s

Energy level (n) of valence electrons is the same as the period of the atom.

Periodic Table shows orbital filling for the electron configuration of elements.

1234567

Draw orbital box and electron config for carbon.

C: 1s2 2s2 2p2

1s 2s 2p

Draw orbital box and electron config for Mg.

Mg: 1s2 2s2 2p6 3s2

1s 2s 2p 3s

Draw electron config for germanium.

Ge – atomic number 32

Ge: 4s2 3d10 4p2

Shorthand notation using noble gas “kernels.”

Ge: [Ar] 4s2 3d10 4p2

1s2 2s2 2p6 3s2 3p6

[Ar]

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Use the periodic table to help write the shorthand configurations for Mn and Ag.

Mn: [Ar] 4s2 3d5 Ag: [Kr] 5s2 4d9

Valence electrons are the electrons found in the outer-most or highest quantum level (n).

F = 9 electrons

1s2 2s2 2p5

The valence configuration is 2s2 2p5

Ge = 32 electrons

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p2

The valence configuration is 4s2 4p2

Valence electrons also removed from highest quantum level (n) in positive ions.

F- = 9 electrons + 1

1s2 2s2 2p5

The ION configuration is 1s2 2s2 2p6

Fe+2 = 26 electrons - 2

1s2 2s2 2p6 3s2 3p6 4s2 3d6

The ION configuration is 1s2 2s2 2p6 3s2 3p6 3d6

Some exceptions to the rule:

Exceptions exist as the energy differences between higher energy sublevels become smaller.

Half-filled and completely filled subshells have extra stability – causes electron promotion.

Cr: [Ar] 4s2 3d4 Cu: [Ar] 4s2 3d9

Actual configurations:Cr: [Ar] 4s1 3d5 Cu: [Ar] 4s1 3d10

4s 3d 4s 3d

Electron promotion accounts for multiple ionization states (Fe+2, Fe+3…)

CAN YOU ? / HAVE YOU?

• Explain the pattern of configuration using the Periodic Table.

• Explain the Aufbau, Pauli and Hund rules.

• Write the electron configuration or orbital box diagrams for a variety of atoms and ions.