JEE Main · 2025 · 22 Jan 2025 · Shift 1 · Classification of Elements and Periodicity

On the Pauling scale, electronegativity rises across a period and falls down a group.

Period 2: Li 1.0, Be 1.5, B 2.0, C 2.5, N 3.0, O 3.5, F 4.0
Period 3: Na 0.9, Mg 1.2, Al 1.5, Si 1.8, P 2.1, S 2.5, Cl 3.0

$Al<Si<C<N$ reads $1.5<1.8<2.5<3.0$ — correct.
$Mg<Be<B<N$ reads $1.2<1.5<2.0<3.0$ — correct.
$S<Cl<O<F$ reads $2.5<3.0<3.5<4.0$ — correct.

For $Al<Mg<B<N$, the actual values give $Al=1.5$ and $Mg=1.2$, so aluminium is more electronegative than magnesium, not less. The true order is $Mg<Al<B<N$, which makes the given sequence $Al<Mg<B<N$ the incorrect one.