Question

Among the second period elements, the actual ionization enthalpies are in order:

Li<B<Be<C<O<N<F<Ne.

Explain why

(i). Be has higher first ionization enthalpy than B?

(ii). O has lower first ionization enthalpy than N and F?

Answer 1

(a).He has higher first ionization enthalpy than B because Be has more stable electronic configuration 1s² 2s² than B 1s² 2s² 2p¹ . 

(b). ∆_iH₁ of O is expected to be more than that of N but is actually lesser because the electronic configuration of N is more symmetrical as well as stable in comparison to O.∆_i H₁ of O is less than that of F because the ionization enthalpy in general increases along a period.