A particular type of multicenter (three center - four electron) $\ce{X–H...Y}$ in which the central hydrogen atom covalently linked to an electronegative atom $\ce{X}$ ($\ce{C}$, $\ce{N}$, $\ce{O}$, $\ce{S}$...) forms an additional weaker bond with atom $\ce{Y}$ ($\ce{N}$, $\ce{O}$, $\ce{S}$...) in the direction of its lone electron pair orbital. The energy of hydrogen bonds, which is usually in the range of \(\pu{3\!{-}\! 15 kcal/mol}\) (\(\pu{12\!{-}\! 65 kJ/mol}\)), results from the electrostatic interaction and also from the orbital interaction of the antibonding $\upsigma^{\ast}(\ce{XH})MO$ of the molecule acting as the hydrogen donor and the non-bonding lone electron pair $MO{\rm{n}}_{\rm{Y}}$ of the hydrogen acceptor molecule.