Question

Pick out the following isoelectronic species with $C{{O}_{2}}$
A. ${{N}_{3}}^{-}$
B. ${{(CNO)}^{-}}$
C. ${{(NCN)}^{2-}}$
D. All of these

Answer 1

Hint: Isoelectronic species are those which have 2 molecules or atoms having equal no of valence electrons present in their orbit. To check for isoelectronic species, we have to check the number of electrons in all the options.

Complete answer:
Isoelectronic series is a group of atoms/ions that have the identical number of electrons. Since the quantity of electrons are the same, size is set by the quantity of protons. Al has 13 protons, therefore the nuclear charge is greatest and pulls the electrons closer, thus is that the smallest.
Elements with similar electronic configurations tend to possess similar chemical and physical properties. it's common for elemental ions to own not only similar but precisely the same electronic configurations as other elements or ions. When two elements and/or ions have similar electron configurations then, they're "isoelectronic" with each other. When two chemical species are isoelectronic they again tend to possess similar chemical properties.
Some Examples of isoelectronic species are ${{O}_{2}}^{-},{{F}^{-}},Ne,N{{a}^{+}},M{{g}^{2+}}\,and\,A{{l}^{3+}}(1{{s}^{2}}2{{s}^{2}}2{{p}^{6}})$
So according to the definitions of isoelectronic species we need to first calculate the total no valence electrons of the species.
In $C{{O}_{2}}$ there are 16 valence electrons . That is 4 valence electrons of carbon and ($2\times 6$) valence electrons of oxygen.
Nitrogen contains 5 valence electrons therefore N3- contains (15+1) 16 valence electrons
Carbon contains four valence electrons, nitrogen consists of five valence electrons and oxygen consists of six valence electrons
Therefore ${{(CNO)}^{-}}$ consists of( 15+1)16 valence electrons
${{(NCN)}^{2-}}$ also contains 16 valence electrons.
Similarly $N{{O}_{2}}^{-}$ contains 18 valence electrons.
So except $N{{O}_{2}}^{-}$ all are Isoelectronic with $C{{O}_{2}}$

Note:
$N{{a}^{+}}$ and ${{F}^{-}}$ ions( both contains 10 electrons): $N{{a}^{+}}$ has 11 protons and a nuclear charge of +11.
We can easily make any adjacent elements of periodic table as isoelectronic species by giving them negative charge to one and positive to another.