The d Block

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Slide 1

The d block

The d block consists of three horizontal series in periods 4, 5 & 6

10 elements in each series

Chemistry is “different” from other elements

Special electronic configurations important

Differences within a group in the d block are less sharp than in s & p block

Similarities across a period are greater

Slide 2

Electronic Configuration

Across the 1st row of the d block (Sc to Zn) each element

has 1 more electron and 1 more proton

Each “additional” electron enters the 3d sub-shell

The core configuration for all the period 4 transition elements is that of Ar

1s22s22p63s23p6

Slide 3

3

1s

2s

3s

4s

2p

3p

3d

Energy

Ar

1s2 2s2 2p6 3s2 3p6

4p

Slide 4

4

1s

2s

3s

4s

2p

3p

3d

Energy

Sc

1s2 2s2 2p6 3s2 3p6 3d1 4s2

4p

Slide 5

5

Slide 6

Chromium and Copper

Cr and Cu don’t fit the pattern of building up the 3d sub-shell, why?

In the ground state electrons are always arranged to give lowest total energy

Electrons are negatively charged and repel each other

Lower total energy is obtained with e- singly in orbitals rather than if they are paired in an orbital

Energies of 3d and 4s orbitals very close together in Period 4

Slide 7

Chromium and Copper

At Cr

Orbital energies such that putting one e- into each 3d and 4s orbital gives lower energy than having 2 e- in the 4s orbital

At Cu

Putting 2 e- into the 4s orbital would give a higher energy than filling the 3d orbitals

Slide 8

8

1s

2s

3s

4s

2p

3p

3d

Energy

Cr

1s2 2s2 2p6 3s2 3p6 3d5 4s1

4p

Slide 9

9

1s

2s

3s

4s

2p

3p

3d

Energy

Cu

1s2 2s2 2p6 3s2 3p6 3d10 4s1

4p

Slide 10

What is a transition metal?

Transition metals [TM’s] have characteristic properties

e.g. coloured compounds, variable oxidation states

These are due to presence of an inner incomplete d sub-shell