Question

: Valency of carbon in carbonate $\text{C}{{\text{O}}_{3}}^{2-}$ ion is:
A.2
B.3
C.4
D.5

Answer 1

The combining capacity of en element is defined by its Valency. The number of covalent bonds formed by the atom in an element in a compound is also expressed by the valency of the element.

Complete step by step answer:
The electronic configuration of carbon atom is: $\text{1}{{\text{s}}^{\text{2}}}\text{2}{{\text{s}}^{\text{2}}}\text{2}{{\text{p}}^{\text{2}}}$. So, in total there are 4 electrons in the valence shell of carbon. As carbon has one vacant “p” orbital so the atomic orbitals hybridize to form four hybrid orbitals with all equal properties and the electron pair in “s'' orbital is unpaired to and are placed in two separate orbitals.
Hence, there are four unpaired electrons which are capable of forming four covalent bonds to the surrounding.
So, the valency of carbon in all its compounds is 4.

The correct option is C.

Note:
Alternatively, the valency of oxygen atom in is 2. Consider the valency of carbon in carbonate to be x. Now, as the total valency of the anion is $\left( { - 2} \right)$ , therefore,
$\text{x}+\left[ \left( -2 \right)\times 3 \right]=-2$
$\Rightarrow \text{x}=6-2=4$
Hence the valency of carbon in carbonate is 4.
The valency of an element is different from the oxidation state of the element. The oxidation number can be positive, negative, or neutral. Nut the valency of the element has no sign. The oxidation number is a hypothetical charge on the atom in a molecule or an ion and it’s also a measure of the apparent capacity of the atom in the species to gain or lose electrons.