Question

Which species does not exist?
A.${\left( {SnC{l_6}} \right)^{2 - }}$
B.${\left( {GeC{l_6}} \right)^{2 - }}$
C.${\left( {CC{l_6}} \right)^{2 - }}$
D.${\left( {SiC{l_6}} \right)^{2 - }}$

Answer 1

Hint:To answer this question, you must recall the formation and properties of a coordinate bond. Atoms of one element bond with another atom of the same or other element in order to fill their outermost shell and gain stability.

Complete answer:
Coordinate bond is a type of covalent bond formed between two different atoms in which the electron pair is shared by both the atoms but both the electrons are shared by only one species. The species that is donating the electron pair is known as a Lewis base and the species that accepts the electron pair is known as a Lewis acid. This bonding is also known as a dative bond.
The given compounds all contain a central atom as group 14 elements. All the elements have 4 valence electrons and can thus easily form 4 covalent bonds and make a species of the form $MC{l_4}$where $M = C,Si,Ge,Sn$. The species given in the question are of the form ${\left( {MC{l_6}} \right)^{2 - }}$ which means that two chlorine atoms form coordinate bonds with the central atom. Thus, the central atom must have vacant orbitals for the chlorine to coordinate the lone pair of electrons.
All the atoms except for carbon have vacant $d - $orbitals. Thus, carbon cannot accept $6$ $C{l^ - }$ and thus the species ${\left( {CC{l_6}} \right)^{2 - }}$ does not exist.

Thus, the correct option is C.

Note:
In a coordinate bond, the species that donates the electron is known as the donor and the species that accepts the electron is known as acceptor or the receptor. A coordinate bond is represented with an arrow from the donor atom pointing towards the acceptor atom. Coordinate bonding is integral to the Lewis theory.