Coordinate Covalent Bond
A covalent bond in which the shared pair of electrons are donated by only one atom and other one only use it is called “Coordinate covalent bond”.
A covalent bond in which the orbital of any atom with lone pair overlaps with orbital of any other atom with no electrons, is said to be co-ordinate covalent bond. Some elements of group VA, VIA and VIIA have lone pairs when present in a stable molecule and thus we that lone pair for sharing with any atom with no electrons and therefore co-Ordinate bonds are formed.
i. Formation of Ammonium Ion:
In ammonium ion which is formed by combination of NH3 and H+, Nitrogen atom present in ammonia have a lone pair. This lone pair is share with H+ ion having no electron; therefore, coordinate covalent bond is formed as;
The atom which donates electrons is called donar while the atom which accept electron is called Acceptor.
Co-ordinate bond is denoted by (–>).
ii. Formation of Hypronium ion