Also because the transition metal ions can change their oxidation states,
they become more effective as catalysts For example, iron(III) catalyses
the reaction between iodide and persulphate ions 2 I
– + S2O8
2– ® I2 + 2 SO4
2–
An explanation of this catalytic action can be given as:
2 Fe
3+ + 2 I
– ® 2 Fe
2+ + I2
2 Fe
2+ + S2O8
2– ® 2 Fe
3+ + 2SO4
2–
Interstitial compounds are those which are formed when small atoms
like H, C or N are trapped inside the crystal lattices of metals They are
usually non stoichiometric and are neither typically ionic nor covalent,
for example, TiC, Mn4N, Fe3H, VH0