JEE Main · 2023 · 01 Feb 2023 · Shift 2 · Atomic Structure

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Which one of the following sets of ions represents a collection of isoelectronic species?
(Given : Atomic Number : F :9, Cl : 17, Na = 11,

Mg = 12, Al = 13, K = 19, Ca = 20, Sc = 21

)

(A) $(Li^{+}, Na^{+}, Mg^{2 +}, Ca^{2 +})$
(B) $(Ba^{2 +}, Sr^{2 +}, K^{+}, Ca^{2 +})$
(C) $(N^{3 -}, O^{2 -}, F^{-}, S^{2 -})$
(D) $(K^{+}, Cl^{-}, Ca^{2 +}, Sc^{3 +})$ ✓ Correct

Answer: (D)

Solution

Isoelectronic species carry the same number of electrons. For the ions

K^{+}

C l^{-}

C a^{2 +}

and

S c^{3 +}

the electron counts are

19 - 1

17 + 1

20 - 2

and

21 - 3

, each equal to eighteen and matching the argon configuration. The other sets combine ions of differing electron counts. The collection in which every ion has eighteen electrons is

K^{+}, C l^{-}, C a^{2 +}, S c^{3 +}

JEE Main · 2023 · 01 Feb 2023 · Shift 2 · Single correct option

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