Bond formation, hydrogen cyanide molecule. Illustration of the sharing of electrons (dots and crosses) between a hydrogen (H), carbon (C) and nitrogen (N) atom to form a molecule of hydrogen cyanide (HCN). This is an example of covalent bonding, with the single bond (left) and the triple bond (right) formed by shared electron pairs, each pair consisting of an electron from each atom. The outer electron shell of each atom is shown as a blue ring. Cyanide is a volatile liquid at room temperature and pressure. The bonds are not shown here. For the fully bonded molecule, see image C028/6481.