Question

Among the following, the isoelectric species is/are
i).${O^{2 - }},{F^ - },M{g^{2 + }},N{a^ + }$
ii).$\;N{a^ + },M{g^{2 + }},A{l^{3 + }},{F^ - }$
iii).${N^{3 - }},{O^{2 - }},{F^ - },Ne$
A) i) and ii)
B) i), ii) and iii)
C) ii) and iii)
D) i) and iii)

Answer 1

For finding the isoelectronic pairs, we can just add the number of electrons of each atom in the species and also the charge of the species (if present). - Then, if the number of electrons is equal in both species, they are said to be isoelectronic pairs.

Complete answer:
We need to remember that isoelectronic refers to two atoms, ions, or molecules that have the same electronic structure and the same number of valence electrons. The term means "equal electric" or "equal charge". We need to remember that the isoelectronic chemical species typically display similar chemical properties. As we know, isoelectronic species are the species belonging to different atoms or ions which have the same number of electrons but different magnitudes of nuclear charge. Now, A positive charge denotes the loss of an electron & A negative charge denotes the gain of an electron by a species.

1. Number of electrons in sodium $\left( {Na} \right) = 11$
   Therefore, Number of electrons in $N{a^ + } = 10$
2. Number of electrons in ${O^{2 - }} = 18$
3. Number of electrons in $M{g^{2 + }} = 10$
4. Number of electrons in ${\text{ }}{F^ - } = 10$
5. Number of electrons in $A{l^{3 + }} = 10$
6. Number of electrons in ${N^{3 - }} = 10$
7. Number of electrons in $Ne = 10$

Therefore, option B is correct.

Note:
We need to remember that isoelectric principle states that “Molecules that have the same number of electrons and the same number of heavy atoms have similar electronic structure and similar. Isoelectronic species are the species belonging to different atoms or ions which have the same number of electrons but different magnitudes of nuclear charge.