Question

Identify the element which has highest second ionization enthalpy:

• A. Carbon
• B. Phosphorus
• C. Nitrogen
• D. Oxygen

Hint:

Second ionization enthalpy depends on effective nuclear charge and atomic size. Higher nuclear charge and smaller size lead to higher ionization energy.

Answer 1

The Correct Option is D

Step 1: Identify the +1 ion with the most stable configuration.
Removing one electron from each neutral atom gives O\(^+\) the configuration [He]2s\(^2\)2p\(^3\) -- exactly half-filled 2p, which is extra stable.

Step 2: Apply the stability rule.
Removing the next electron from O\(^+\) disrupts this stable half-filled arrangement, requiring exceptional energy. Oxygen has the highest 2nd IE among the four.
\[ \boxed{\text{Oxygen}} \]