Question

explain why does carbon forms only covalent

Answer 1

Because carbon has 4 electrons in its outermost shell (and because eachcovalent bond requires a donation of 1 electron, per atom, to the bond) carbonhas exactly four bonds to make, and isonly stable if all 4 of these bonds are used. This same rule applies to all of the atoms in the second row of the periodic table.

Answer 2

because it has 4 electrons in its outer most shell. carbon require more energy to loss or gain 4 electrons. so it nor losses neither gain electrons but share them with other elements and complete its octet. so it form covalent bond.