Hydrogen bond
Hydrogen bonds can vary in strength from weak (1–2 kJ mol) to strong (161.5 kJ mol in the ion ). Typical enthalpies in vapor include:
Alkene
Like a single covalent bond, double bonds can be described in terms of overlapping atomic orbitals, except that, unlike a single bond (which consists of a single sigma bond), a carbon–carbon double bond consists of one sigma bond and one pi bond. This double bond is stronger than a single covalent bond (611 kJ/mol for C=C vs. 347 kJ/mol for C–C) and also shorter, with an average bond length of 1.33 ångströms (133 pm).