Question

How enthalpy of atomisation determines the standard electrode potential of elements?

Answer 1

Think of an enthalpy cycle (Hess's Law assuming standard conditions).

The first step will be enthalpy of atomisation (∆H_atom)

Solid metal → gaseous metal atoms

The second step would be to find the ionisation energy (IE),

Gaseous metal atoms → gaseous metal ions

Then you find enthalpy of hydration (∆H_hydration).

Gaseous metal ions → gaseous metal ions in solution

The electrode potential is the net sum of the energy of these changes. It can be measured in a hydrogen cell.

2H+(aq) + M(s) reversible M2+(aq) + H2 (g)

By calculating ∆H of atomisation we can actually see how stable the oxidation state of that particular transition element is in aqueous solution. The smaller the value of energy change for that particular oxidation state, he greater its stability.

Transition elements generally have large enthalpies of atomisation and ionisation energies. Therefore they are very stable.