MM 2007 AH

Quantum numbers

3

3

3

2

2

1

Value of n

2

1

0

1

0

0

Value of l

-2, -1, 0, +1, +2

-1, 0, +1

0

-1, 0, +1

0

0

Value of m1

3d

3p

3s

2p

2s

1s

Type of atomic orbital

5

3

1

3

1

1

Number of orbitals

n

l

m1

ms

principal

angular momentum

magnetic

spin

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Pauli Exclusion Principle

No 2 electrons in any one atom can have the same set of

four quantum numbers

• the maximum number of electrons in any orbital is 2

• 2 electrons occupying the same orbital must have opposite spin

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Electronic configuration

H 1s1 or

1s

He 1s2 or

1s

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Aufbau principle• Lowest energy orbitals filled first

• Electrons assigned to orbitals in order of increasing n + l

• Where 2 subshells have same n + l, that with lowest n filled first

Hund’s rule of maximum multiplicityDegenerate orbitals occupied singly, with electrons keeping their spin

parallel before spin pairing occurs

N 1s2 2s2 2p3

1s 2s 2p

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Electronic arrangement of Noble gases

Ne 1s2 2s2 2p6

Ar 1s2 2s2 2p6 3s2 3p6

Electronic configuration of other elements can be abbreviated

taking account of previous Noble gas

e.g. magnesium [Ne] 3s2

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Periodic table blocksPeriodic table subdivided into s, p, d and f blocks

depending on which subshell occupied by outermost electrons

s-block

d-blockp-block

f-blockN 1s2 2s2 2p3Na 1s2 2s2 2p6 3s1

MM 2007 AH

Ionisation energies

E (g) E+ (g) + e-

E+ (g) E2+ (g) + e-

Three main factors affecting ionisation energies

• atomic size

• nuclear charge

• screening effect

- the bigger the smaller!

- the bigger the bigger!

- the bigger the smaller!

MM 2007 AH

First ionisation energies

Be 1s2 2s2

B 1s2 2s2 2p1

N 1s2 2s2 2p3

O 1s2 2s2 2p4

In general,across a period …down a group ….

ionisation energy increases

He 1s2

Ne 1s2 2s2 2p6

Ar 1s2 2s2 2p6 3s2 3p6

Second and third ionisation energies?

ionisation energy decreases

MM 2007 AH

Spectroscopy

Atomic emission spectroscopy

Spectral lines correspond to transitions between energy levels

Lines usually in visible of UV region of electromagnetic spectrum

• gaseous sample excited with

thermal or electrical energy

• qualitative and quantitative -

intensity of radiation increases

with amount of element

• helium discovered using this

technique - Sir Norman Lockyer

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Spectroscopy

Atomic absorption spectroscopy

• radiation passed through

gaseous sample of substance

• qualitative and quantitative -

absorbance proportional to

concentration of element

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Atomic absorption spectroscopy

0

20

40

60

80

0 10 20 30 40 50 60

Concentration

Absorbance

Calibration curve

Allows determination of concentrations of elements in samples