Question

Which of the following elements will have highest ionisation energy?

• A. $1s^{2}2s^{2}2p^{6}3s^1$
• B. $1s^{2}2s^{2}2p^{6}3s^{2}3p^3$
• C. $1s^{2}2s^{2}2p^{6}3s^{2}3p^4$
• D. $1s^{2}2s^{2}2p^{6}3s^{2}3p^1$

Answer 1

The correct option is B $1s^{2}2s^{2}2p^{6}3s^{2}3p^3$

Element with electronic configuration $1s^{2}2s^{2}2p^{6}3s^{2}3p^3$ will have highest ionisation energy. 3p orbital is half filled and stable. Removal of electron from stable, half filled p orbital requires more energy. Also, on moving from left to right in a period, the ionisation energy increases.