Which one of the following groupings represents a collection of isoelectronic species?

(At. nos.: Cs-­55, Br­-35)

  • Option 1)

    Na^{+},Ca^{2+},Mg^{2+}\;

  • Option 2)

    \; N^{3-},F^{-},Na^{+}\;

  • Option 3)

    \; Be,Al^{3+},Cl^{-}\;

  • Option 4)

    \; Ca^{2+},Cs^{+},Br.

 

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.

- wherein

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

 

 We know that the isoelectronic species have the same number of electrons.

Let us take the options one by one:

Na^{+}: 10\:\:\:\:\:\:\:\:\:\:\:\:\:\:N^{3-}:10\:\:\:\:\:\:\:\:\:\:\:\:\:\:Be:4

Ca^{2+}: 18\:\:\:\:\:\:\:\:\:\:\:\:\:\:F^{-}:10\:\:\:\:\:\:\:\:\:\:\:\:\:\:A1^{3+}:10

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

 

Ca^{2+}:18

Cs^{+}:54

Br\::\:35

Clearly, \; N^{3-},F^{-},Na^{+}\; are isoelectronic species.

 

 


Option 1)

Na^{+},Ca^{2+},Mg^{2+}\;

This option is incorrect.

Option 2)

\; N^{3-},F^{-},Na^{+}\;

This option is correct.

Option 3)

\; Be,Al^{3+},Cl^{-}\;

This option is incorrect.

Option 4)

\; Ca^{2+},Cs^{+},Br.

This option is incorrect.

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