Question

Which of the following configuration has highest ionisation energy?

• A. $1s^{2}2s^{2}2p^{1}$
• B. $1s^{2}2s^{2}2p^{3}$
• C. $1s^{2}2s^{2}2p^{2}$
• D. $1s^{2}2s^{2}2p^{4}$

Answer 1

Answer: (B)

$2s^{2}2p^{3 }$ is stable configuration because the outer sub-shell is half-filled. Half filled configurations are stable configurations. The one half-filled and one completely filled orbital gives stability. Hence, $2s^{2}2p^{3}$ has the highest ionization energy among the given elements. Due to high stability of half-filled orbitals, it has high ionisation energy.