Electron sharing can be depicted by a Lewis dot structure, in which element symbols are surrounded by dots that represent the valence electrons (electrons in the shell). A bond is the sharing of a pair of valence electrons by atoms. Hydrogen has valence electron(s) in the first shell, but the capacity of the shell is electron(s). When a hydrogen atom comes close enough to a carbon atom for their orbitals to overlap, they can share their electrons. The hydrogen atom is now associated with electron(s) and a bond is formed. As a result, one of the structures does not make sense because hydrogen has only valence electron(s) to share, so it cannot form bonds with two atoms.