Chemistry, Third edition

206 12 · CHEMICAL FAMILIES

4.Many of the metals can exist in a wide range of oxidation states. These are shown

in Box 12.8. The 3d electrons are very close in energy to the 4s electrons and both

types of electrons can be involved in bonding.

0.Notice that the later metals in the series do not display anywhere near the maxi-

mum oxidation states possible. This is because the nuclear charge increases

across the series and the outer electrons are held more tightly to the atoms.

BOX 12.7

Changes across the first transition series

Element Ti V Cr Mn Fe Co Ni Cu

Electronic [Ar]3d^2 4s^2 [Ar]3d^3 4s^2 [Ar]3d^5 4s^1 [Ar]3d^5 4s^2 [Ar]3d^6 4s^2 [Ar]3d^7 4s^2 [Ar]3d^8 4s^2 [Ar]3d^10 4s^1

structure

Atomic 1146 1131 1125 1129 1126 1125 1124 1128

radius/pm

First ionization 1658 1650 1653 1717 1759 1758 1737 1746

energy

/kJ mol^1

Melting 1930 2160 2130 1520 1800 1770 1730 1360

point/K

Magnetic

properties of the

d-block elements

Write down the electronic

configurations (‘electrons

in boxes’) of the following

metals and decide whether

the metals are paramagnetic

or diamagnetic:

(i)V(ii)Cr(iii)Zn.

Which metal do you think

shows the strongest

paramagnetism?

Exercise 12M

BOX 12.8

Oxidation numbers of the d-block elements

Metal ScTi V Cr MnFe CoNi CuZn

7

6 66

Oxidation 5 5555

states 444 4 444

3333 3 3333

222222222

11111111

(Important oxidation numbers are in bold type.)

3.Metallic Fe, Co and Ni are ferromagnetic– they are able to become permanently

magnetized. Other metals and their compounds are paramagnetic– they are

weakly attracted into a magnetic field. Paramagnetism is caused by the presence

ofunpairedspinning electrons. Two electrons paired up, in the same orbital, spin

in opposite directions and their moments cancel each other out. If a substance

has all its electrons paired up it is termed diamagnetic, and the substance is not

attracted into a magnetic field.

5.Many transition metals, or their compounds, are important catalysts. For

example, Fe is used as a catalyst in the Haber process to synthesize ammonia:

N 2 (g)3H 2 (g)\==\2NH 3 (g)

0.When the substance acts as a catalyst, bonds are formed between atoms of the

reactants and the catalyst surface, so weakening the bonds in the reactants. A