Question

How many sigma and pi bonds are present in tetra cyano methane?

Answer 1

The total number of bonds in any compound is the sum of total sigma bonds and pi bonds. The molecular formula of tetra cyano methane is $C{(CN)_4}$.

Complete step-by-step answer: Tetra cyano methane is also known as carbon tetracyanide. It is a per cyano alkane with molecular formula $C{(CN)_4}$. The structure can be considered as methane with all hydrogen atoms replaced by cyanide groups. Tetra cyano methane is a solid at room temperature. It decomposes over 160 °C without melting, and although it can be in a dilute vapour, no liquid form is known.
The molecules of tetra cyano methane have a tetrahedral geometry with carbon atoms at the centre and four CN atoms surrounding it. The C-C bond length is 1.484 and the C≡N bond length is 1.161 in the gas form. In the solid the C≡N bond shortens to 1.147. At pressures over 7 GPa tetra cyano methane starts to polymerize to form a disorganised covalent network solid. At higher pressure the colour yellows and darkens to black.
The structure of tetra cyano methane is:

As clearly seen from the structure, there are four C-C sigma bonds and four C-N sigma bonds. So, there are a total of eight sigma bonds. And there are eight C-N pi bonds. So, there are a total of eight pi bonds. Hence, there are a total of 16 bonds in tetra cyano methane.

Note: When asked about the total bonds of $C{(CN)_4}$, a student can forget to count the bonds between carbon and nitrogen. Then his incorrect answer would come out to be 4.