Question

How many double covalent bonds can a single carbon atom form at a time?
A) 1
B) 2
C) 3
D) 4

Answer 1

Hint: Carbon atoms have a valency of four. This means that it can accept four electrons and form ionic bonds or it can share its four electrons and form four covalent bonds. Covalent bonds are formed by the sharing of electrons.

Complete answer:
Carbon is a nonmetal with the atomic number six. The electronic configuration of carbon is - $1s^{2}2s^{2}2p^2$ . There are four electrons present in the outermost shell of carbon that participates in bond formation. Carbon usually forms covalent bonds (single, double, and triple bonds). The single bond between two carbons is a sigma bond, while the double bond contains one sigma and one pi bond, two pi and one sigma bond in a triple bond.
In $H_{2}C=C=C{H}_2$ , the carbon can be seen as having two double bonds. As the valency is four only, it can not form any more bonds further.
Hence, it can be concluded that a single carbon can form two double covalent bonds at a time.
So, option B) is the correct answer.

Note:
The orbitals which are involved in the double bond are s and p. The hybridization of carbon that has two double bonds is sp hybridization, while the carbon having a single bond has $s{p}^2$ hybridization.