Question

The first ionization potential of Mg, Al, P, and S follows the order:

• A. Mg < Al < P < S
• B. Al < Mg < P < S
• C. Al < Mg < S < P
• D. Mg < Al < S < P

Hint:

Look for exceptions in the period 3 ionization energy trend caused by stable electron configurations.

Answer 1

The Correct Option is C

Step 1: Mg [Ne]3s2 (filled), Al [Ne]3s2 3p1 (single p e-, easier removal). Al<Mg.

Step 2: P [Ne]3s2 3p3 (half-filled, stable), S [Ne]3s2 3p4 (paired e-, easier removal). S<P.

Step 3: Combined: Al(578)<Mg(738)<S(1000)<P(1012).

\[\boxed{\text{Al} < \text{Mg} < \text{S} < \text{P}}\]