# What is the total number of electrons shared in the bonds between the two carbon atoms in a molecule of H-C=C-H?

In acetylene, $H C \equiv C H$, or ethylene, ${H}_{2} C = C {H}_{2}$?
Each carbon atom has 4 valence electrons. In acetylene, there are 3 carbon-carbon bonds, i.e. 6 electrons shared between the carbons. And in ethylene there are 4 electrons shared between the carbon atoms; the remaining 2 electrons constitute half of the $C - H$ bonds.