Question

How many $\sigma -$ and $\pi -$ bonds are there in the molecule of tetracyanoethylene?
A.nine $\sigma -$ and nine $\pi$
B.five $\sigma -$ and nine $\pi$
C.nine $\sigma -$ and seven $\pi$
D.five $\sigma -$ and eight $\pi$

Answer 1

Chemical bond plays a major role in the formation of a new compound or stable element. It is an attraction between ions, atoms, and molecules. During the formation of bonds, the element may gains, losses, and shares its atom with the respective element.

Complete step by step answer:
Before calculating the $\sigma$ and $\pi$ bonds in the molecule of tetracyanoethylene, let's discuss the types of chemical bonds.
Well, there are many types of chemical bonds but two main bonds are important, and the rest subpart of them. These are the ionic bond, chemical bond.
Ionic bond - During the formation of this bond, elements gain or lose its atom with respective elements to complete octet and become stable.
Covalent bond - During the formation of this bond, the element shares its atom with the respective element to complete its octet and become stable.
Now, come to the $\sigma$ and $\pi$ bond, these are the types of the covalent bond.
$\sigma$ bond - When head-on overlapping between atomic orbital then this bond is formed.
$\pi$ bond - When sidewise overlapping between atomic orbital in a lateral form then this bond is formed.
Now, come to the tetracyanoethylene and its bond.
tetracyanoethylene - It is a chemical compound that is organic. And it is generally available in solid-state. Its chemical formula is ${C_2}{(CN)_4}$

chemical structure -

$$N \equiv {C_\backslash }\,\,\,\,\,\,\,\,\,\,\,\,{}_/C \equiv N \\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,C = C \\\ N \equiv {C^/}\,\,\,\,\,\,\,\,\,\,\,{}^\backslash C \equiv N \\\$$

Each triple bond has $1\,\sigma$ ,and $2\,\pi$. Double bond has $1\,\sigma$ and $1\,\pi$ . And the single bond has $1\,\sigma$ .
Firstly calculate the $\sigma$ bond.
We have four triple bonds, which means four $\sigma$ bonds likewise, one double bond has $1\sigma$ and four single bonds have four $\sigma$ so total $9\,\sigma$ bonds.
$\pi$ bonds - We have four triple bonds, which means eight $\pi$ bonds likewise, one double bond has $1\,\pi$ and so total $9\,\pi$ bonds.
Now, we got nine $\,\pi$ and nine$\,\sigma$ bonds in molecules of tetracyanoethylene.
Therefore, the option $A$is the correct answer.

Note:
$\sigma$ bond is a very strong bond. It has three types that are S-S overlapping, S-P overlapping, and P-P overlapping. $\pi$ bond is weak as compared to $\sigma$ bond. Organic compound - The compound that is formed by the hydrogen-carbon bond.