Alkanes are relatively small molecules in which all the chemical bonds are covalent bonds. All the bonds in alkane molecules are single bonds i.e. C C carbon carbon or C H carbon hydrogen. Each carbon atom forms four single covalent bonds and hydrogen atoms form one single covalent bond. All single bonds are formed by sharing a pair of electrons e.g. one from each of a carbon atom and a hydrogen atom, or two carbon atoms contributing (sharing) an electron each to the covalent bond.