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NEET levelSingle correct optionDifficulty 1 of 3sb112

Which of the following compounds is paramagnetic?

A $KO X_{2}$
B $Na X_{2} O X_{2}$
C $Li X_{2} O$
D $CaO$

Answer: A

KO X_{2}

contains the superoxide ion

O X_{2} X^{-}

, which has one unpaired electron in a

π^{*}

orbital.

Na X_{2} O X_{2}

has the peroxide ion

O X_{2} X^{2 -}

with all electrons paired, and

Li X_{2} O

and

CaO

contain

O X^{2 -}

(closed shell). So only

KO X_{2}

is paramagnetic.

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