Question

The correct order of first ionization energy is:

• A. $Be<B<N<O$
• B. $B<Be<N<O$
• C. $B<Be<O<N$
• D. $O<N<B<Be$

Answer 1

Answer: (C)

lionization energy generally increase from left to right in a period. Hence expected increasing order is Be, B, N, O but the actual order, found is: B < Be < O < N The reason is that Be and N, have comparatively stabler electronic configurations ( $n{s}^2$ and $n{p}^3$ ) than those of B and O ( $n{p}^1$ and $n{p}^4$ ). Hence, their ionisation energy becomes higher.