(i) Hydrogen bond involves dipole attractions.
(ii) It is formed between hydrogen atom and a highly electronegative atom (F, O or N).
(iii) Strength of hydrogen bond is very small e.g., bond strength of H.F bond is 41.83 kj
Covalent bond :
Covalent bond involves sharing of electrons.
It is formed between any two electronegative atoms which may be of the same element or of different elements.
Bond Strength of covalent bond is sufficiently high. For example, bond strength of H—H bond is 433 kj