In case of bond formation in Acetylene molecule : a. How many covalend bonds are formed ?

Acetylene (\(\mathrm{H{-}C{\equiv}C{-}H}\)): a. 5 covalent bonds; b. 3 σ bonds and 2 π bonds; c. sp hybridisation.

a. There are two C–H single bonds and one C≡C triple bond. Counting each bond in the triple bond, that is 2 + 3 = 5 covalent bonds.

b. σ bonds: 2 C–H + 1 C–C = 3. π bonds: the remaining 2 bonds of the triple bond = 2.

c. Each carbon is sp hybridised: its 2s and one 2p orbital mix to form two sp orbitals at 180°. One sp orbital of each C overlaps with the other carbon (C–C σ bond), and the other with the 1s orbital of H (C–H σ bond). The two unhybridised 2p orbitals on each C overlap sideways to form the two π bonds. Hence acetylene is a linear molecule with bond angles of 180°.