Question

How might successive electron affinities be found?

Answer 1

Electron affinity or electron gain enthalpy is defined as the amount of energy released when an extra electron is added to an isolated neutral gaseous atom to form gaseous anion.

The first electron affinity is taken as negative because an atom has an natural tendency to accept electron but the addition of subsequent electron takes place with absorption of energy. Here energy is supplied to overcome the force of repulsion between anion and the added electron.

Example-

O(g)+e– ----------> O–(g) ; ∆H=-141KJ/mol (energy released)

O– (g)+ e– ------------> O²–(g); ∆H= +780KJ/mol (energy absorbed)