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JEE Main levelOne or more correct optionsDifficulty 2 of 3pt087

Consider the species $N X^{3 -}$ , $O X^{2 -}$ , $F X^{-}$ , $Na X^{+}$ , $Mg X^{2 +}$ and $Al X^{3 +}$ . Which statements are correct?

AAll six species are isoelectronic with neon.
B $N X^{3 -}$ has the smallest radius because it has the fewest protons.
CAll six have the same radius because they have the same number of electrons.
D $N X^{3 -}$ has the largest radius and $Al X^{3 +}$ the smallest.

Answer: A, D

Each has

10

electrons. Nuclear charge rises from

7

(

N X^{3 -}

) to

13

(

Al X^{3 +}

), pulling the same electron cloud closer, so radius falls from

N X^{3 -}

to

Al X^{3 +}

. Fewer protons give a larger, not smaller, radius.

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