Hi,

There is no 4 bond formed between carbon because of the carbon electron orbitals. Since it has 4 valence electrons, it needs 4 more to electrons to fill its outer energy level.

It does so by forming covalent bonds with another element, in order to complete its Octet rule.

As per Lewis theory studied in the Nature of Chemical Bonds as per that rule, Carbon can easily form a 4 bond ie tetrabond with other carbon atoms as its valency iss also 4. This satisifies the Octet rule. But the reason it doesn't is defined as you go deep into the chemistry. Things will get more clear to you as you read more and more. Carbon cannot form quadraple bond is based on the concept of hybridization. It does not possess enough atomic orbitals for the same. When in sp hybridisation, it leaves 2 p orbitals over and when it is in sp2 hybridization one p orbital is left. This implies that carbon is stable at C2 just as Nitrogen (N2).

Thank you,