(i) Define coordinate covalent bond.
(ii) strate the formation of coordinate covalent bond with a suitable example.

Explanation

(i) In the bond formation, one of the combining atoms donates a pair of electrons 1.e., two CIectrons which are necessary for the covalent bond formation and these electrons are shared by both the combining atoms, and the bond formed is called coordinate covalent bond.
(ii) e combining atom which donates the pair of electron is called the donor atom and the Otner atom is called the acceptor atom. This bond is denoted by an arrow starting from the donor atom pointing towards the acceptor atom.
(iii) For example, in ferricyanide ion `[Fe(CN)_(6)]^(4-)` each cyanide ion (CN) donates a pair of electrons to form a coordinate bond with iron `(Fe^(2+))` and these electrons are shared by `Fe^(2+) and CN^(-)` ions.
(iv)
(v) Ammonia having a lone pair of electrons donates its pair to an electron deficient molecule such as `BF_(3)` to form a coordinate covalent bond.