CO-ORDINATE COVALENT OR DATIVE COVALENT BOND, MOLECULAR ADDITION COMPOUNDS, FORMATION OF AMMONIUM ION, The nitrogen atom in an ammonia molecule has a lone-pair of electrons

 

CO-ORDINATE COVALENT OR DATIVE COVALENT BOND:

             Atoms in molecules sometimes have pairs of electrons in their valence shell which are not involved in covalent bond. These non-bonding pairs of electrons are called lone pairs. Anion (Negatively charged ions) also have lone-pairs of electrons. These type of covalent bonding in which lone-pair is the shared pair is the shared pair of electrons. i.e; one atom of a molecule or anion donate its lone-pair of electrons for bonding and other atom accept this lone pair in its empty orbital but it remains commonly shared pair of electrons, such type of covalent bonding is called dative or co-ordinate covalent bonding. The word “dative” is derived from latin meaning “give”. The concept of this type of bonding is also the same i.e; one atom donate its lone-pair of electrons for bonding and it is called donor which the other atom which accept this lone-pair of electrons is called accepter. The accepter may be electron pair deficient atom in a molecule or a metal cation or transition metal ion. Dative covalent bond is represented by an arrow which is directed from donor towards acceptor.

             Dative covalent bonding plays an important role the formation of molecular addition compounds and also in the formation of transition metal complex ions.

 MOLECULAR ADDITION COMPOUNDS:

             Such compounds are formed to dative covalent bonding.

 FORMATION OF AMMONIUM ION:

             The nitrogen atom in an ammonia molecule has a lone-pair of electrons. Hence dative covalent bond formed between nitrogen atom of ammonia and hydrogen ion to form ammonium ion, NH⁺₄ is due to dative covalent bonding because both electrons come from the nitrogen atom i.e; lone-pair of nitrogen atom.