Which one of the following sets of ions represents the collection of isoelectronic species?

 

(Atomic nos.: F = 9, Cl = 17, Na = 11, Mg = 12, Al = 13, K = 19, Ca = 20, Sc = 21)

  • Option 1)

    K^{+},Ca^{2+},Sc^{3+},Cl^{-}\;

  • Option 2)

    \; Na^{+},Ca^{2+},Sc^{3+},F^{-}\;

  • Option 3)

    \; K^{+},Cl^{-},Mg^{2+},Sc^{3+}\;

  • Option 4)

    \; Na^{+},Mg^{2+},A1^{3+},Cl^{-}

 

Answers (1)

As we learnt in

Isoelectronic species -

A series of atom, ions and molecules in which each species contains the same number of electrons but different nuclear charge.

e.g.\:\:N^{3-},O^{2-},F^{-},Ne,Na^{+},Mg^{2+},Al^{3+}

 

 Let us consider the number of electrons in all species:

 

K^{+}: 18\:\:\:\:\:\:\:\:\:\:\:\:Na^{+}:10\:\:\:\:\:\:\:\:\:\:\:\:K^{+}:18\:\:\:\:\:\:\:\:\:\:\:\:Na^{+}:10

Ca^{2+}: 18\:\:\:\:\:\:\:\:\:\:Ca^{2+}:18\:\:\:\:\:\:\:\:\:\:Cl^{-}:18\:\:\:\:\:\:\:\:\:\:Mg^{2+}:10

Sc^{3+}: 18\:\:\:\:\:\:\:\:\:\:Sc^{3+}:18\:\:\:\:\:\:\:\:\:\:Mg^{2+}:10\:\:\:\:\:\:\:\:\:\:Al^{3+}:10

Cl^{-}: 18\:\:\:\:\:\:\:\:\:\:\:\:\:F^{-}:10\:\:\:\:\:\:\:\:\:\:\:\:Sc^{3+}:18\:\:\:\:\:\:\:\:\:\:\:\:Cl^{-}:18

 

Clearly, the answer is K^{+},Ca^{2+},Sc^{3+},Cl^{-}\;


Option 1)

K^{+},Ca^{2+},Sc^{3+},Cl^{-}\;

This option is correct.

Option 2)

\; Na^{+},Ca^{2+},Sc^{3+},F^{-}\;

This option is incorrect.

Option 3)

\; K^{+},Cl^{-},Mg^{2+},Sc^{3+}\;

This option is incorrect.

Option 4)

\; Na^{+},Mg^{2+},A1^{3+},Cl^{-}

This option is incorrect.

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