CBSE Class 11-science Answered
Coordinate bond is formed when the shared pair of electrons is provided by one of the two atoms and it is shared by both the atoms. The conditions necessary for the formation of coordinate bond are:
(1). One of the atoms should have a lone pair of electron to share which is known as donor atom.
(2). The other atom must have an incomplete outermost shell which shares the electron pair is known as the acceptor atom.
(3). An arrow pointing from donor towards the acceptor atom represents a coordinate bond.
For example: when BF3 combines with NH3, the nitrogen atom has a complete octet around it, but boron atom has only six electrons around it. The nitrogen atom therefore donates its lone pair of electrons to boron so that its atoms also acquire the octet. This one-sided sharing between N and B atoms gives rise to a coordinate bond.