JEE Main 2025 · 22 January · morning · Single correct · +4 / −1
Which of the following electronegativity order is incorrect?
- (a) S<Cl<O<F
- (b) Al<Si<C<N
- (c) Al<Mg<B<N
- (d) Mg<Be<B<N
Answer and solution
Answer (c) Al<Mg<B<N
Solution
Chemistry ma’am · 3 steps
Electronegativity rises across a period, so Mg must sit below Al, not above it.
- Two trends. Electronegativity increases left to right across a period, because nuclear charge rises while the size shrinks. It decreases down a group, because the bonding electrons sit farther from the nucleus.
Option Pauling values Order given is (a) S 2.58, Cl 3.16, O 3.44, F 3.98 correct (b) Al 1.61, Si 1.90, C 2.55, N 3.04 correct (c) Al 1.61, Mg 1.31, B 2.04, N 3.04 incorrect: Al is not less than Mg (d) Mg 1.31, Be 1.57, B 2.04, N 3.04 correct - Where (c) fails. Mg (group 2) and Al (group 13) are both in period 3. Al is to the right of Mg, so Al is more electronegative. The true order is Mg < Al < B < N.
- So. The incorrect order is (c).
The idea to keep. For electronegativity orders, place each element in the table first: rightward means larger, downward means smaller. Swaps between neighbours in the same period are the usual trick.
Answer from the NTA final answer key. Solution by PrepWiser.