JEE Main 2026 — Apr 2, Shift 1 — Chemistry solution

JEE Main2026Apr 2, Shift 1Chemistry

Given below are two statements :

Statement (I) : The correct sequence of bond lengths in the following species is :

$O_{2}^{+} < O_{2} < O_{2}^{-} < O_{2}^{2 -}$

Statement (II) : The correct sequence of number of unpaired electrons in the following species is :

$O_{2} > O_{2}^{+} > O_{2}^{-} > O_{2}^{2 -}$

In the light of the above statements, choose the correct answer from the options given below :

A
Both Statement I and Statement II are true
B
Both Statement I and Statement II are false
C
Statement I is true but Statement II is false
D
Statement I is false but Statement II is true

Solution

Using molecular orbital theory, the bond orders and unpaired-electron counts are:

Species	Bond order	Unpaired electrons
$O_{2}^{+}$	$2.5$	$1$
$O_{2}$	$2$	$2$
$O_{2}^{-}$	$1.5$	$1$
$O_{2}^{2 -}$	$1$	$0$

Bond length varies inversely with bond order, so bond length order is $O_{2}^{+} < O_{2} < O_{2}^{-} < O_{2}^{2 -}$ — Statement I is true.

The unpaired-electron order is $O_{2} (2) > O_{2}^{+} (1) = O_{2}^{-} (1) > O_{2}^{2 -} (0)$ . Statement II claims $O_{2}^{+} > O_{2}^{-}$ , which is incorrect (they are equal), so Statement II is false.

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