why H-atom alone is not capable of forming hydrogen bond

why H-atom alone is not capable of forming hydrogen bond


1 Answers

Aarti Gupta
askIITians Faculty 300 Points
8 years ago
Hydrogen bonding is an special type of dipole-dipole attraction which is generally stronger than ordinary dipole-dipole and dispersion forces but weaker than covalent and ionic bond.It occurs when a H-atom is bonded to a strongly electronegative atom exists in the vicinity of another electronegative atom with a lone pair of electrons. For this bond to occur there must be an -
1.hydrogen donor and an
2.hydrogen acceptor.
Hydrogen donor is the atom to which the hydrogen atom participating in the hydrogen bond is covalently bonded, which is usually a strongly electronegative atom like N, O, or F. The hydrogen acceptor is the neighboring electronegative ion or molecule, and must posses a lone electron pair in order to form a hydrogen bond.Since the hydrogen donor is strongly electronegative, it pulls the covalently bonded electron pair closer to its nucleus, and away from the hydrogen atom,due to which the H-atom is then left with a partial positive charge, creating a dipole-dipole attraction between the hydrogen atom bonded to the donor, and the lone electron pair on the acceptor.Thus there must be difference in electronegativities of atom and hydrogen.Due to this reason H alone cannot formed hydrogen bonding.

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