Why 2 carbon atoms cant form 4 bonds between them?

Answer 1

When carbon atom undergoes sp hybridization there will be two unchanged p orbitals (Px and Py considering z-axis as molecular axis) and two sp orbitals(hybridized orbitals).

Mechanism of sp hybridization: The ground state carbon atom has 2 es in the 2s orbital and 2 es in the 2p orbital.On excitation the one of the 2s electron is transferred to an empty 2p orbital( say 2pz).Then the half filled 2s orbital and 2pz orbital undergo hybridization yo form to two equivalent sp orbitals(on the molecular axis).

The will be a maximum of 3 bonds that 2 carbon atoms can make: It can be explained by the sp hybridization.When two sp hybridized carbon atoms combine through the z-axis as molecular axis then the unchanged p orbitals undergo lateral overlap forming 2 pi orbitals and one sp orbitals of each carbon atom overlap horizontally forming a sigma orbital.But the other sp orbital of carbon atom cannot overlap since the sp orbitals lie in the same molecular axis.This prevents the formation of the fourth bond.

Answer 2

Each carbon atom can form a total of 4 bonds due to its 4 valence electrons. When 2 carbon atoms come together to bond, they share electrons, forming just 2 bonds between them because they are each contributing 2 electrons to the bond. This allows each carbon atom to achieve a stable electron configuration with a total of 8 electrons around it.

Answer 3

It is not stable by nature. It is also not a diatomic molecule.