Question

The decreasing order of first ionization enthalpy of the following elements is:

• A. \( N>O>C>Be \)
• B. \( O>N>C>Be \)
• C. \( Be>C>O>N \)
• D. \( N>O>Be>C \)
• E.

Hint:

Elements with half-filled or fully filled orbitals have **higher ionization enthalpy** due to extra stability.

Answer 1

The Correct Option is A

Ionization enthalpy generally increases across a period due to increasing effective nuclear charge. 
However, nitrogen has a half-filled p-orbital configuration (2p\(^3\)), which provides extra stability, making its ionization enthalpy higher than oxygen. 
Thus, the correct order is: \[ N > O > C > Be \]