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.