CO-Ordinate Covalency
Chemical Bonding of Class 11
CO - ORDINATE COVALENCY
A covalent bond results from the sharing of pair of electrons between two atoms where each atom contributes one electron to the bond. It is also possible to have an electron pair bond where both electrons originate from one atom and none from the other. Such bonds are called coordinate bond or dative bonds. Since in coordinate bonds two electrons are shared by two atoms, they differ from normal covalent-bond only in the way they are formed and once formed they are identical to normal covalent –bond.
If is represented as→ Atom/ion/molecule donating electron pair is called Donor or Lewis base. Atom / ion / molecule accepting electron pair is called Acceptor or Lewis acid [→] points donor to acceptor
NH4+: NH3 has three (N – H) bond & one lone pair on N – atom. In NH4+ formation this lone pair is donated to H+ (having no election)
NH3 + H+ → NH4+
Lewis base Lewis acid
Properties of the coordinate compounds are intermediates of ionic and covalent compounds. Comparison of ionic, covalent & coordinate compounds
| Sl.no. | Ionic | Covalent | Coordinate |
|---|---|---|---|
| 1. binding force | between ions strong (coulombic) | Between molecules smaller (Vander Waal’s) | in between |
| 2. mp/bp | High | less than ionic | in between |
| 3. condition |
conductor of electricity in fused state & in aqueous solution |
bad conductor | Greater than covalent |
| 4. solubility in polar solvent (H2O) | High | Less | in between |
| 5. Solubility in non polar solvent (ether) | Low | High | in between |
| 6. Physical state | Generally solid | liquid & gaseous | solid, liquid gas |
