Group 15 elements

Basic Points of group 15 elements

1. Group 15 Elements Nitrogen Family

2.  Group 15 or the Nitrogen family Consist of : Nitrogen(N) Phosphorus(P) Arsenic(As) Antimony(Sb) Bismuth(Bi)

3. Group 15 consist of metal ,non-metal and metalloids. Nitrogen(N ) - non-metal Phosphorus(P ) - non-metal Arsenic(As) - metalloid Antimony(Sb ) - metalloid Bismuth(Bi ) - metal

4.  Nitrogen comprises 78% by volume of the atmosphere Nitrogen also found in form of protein in plants and animals. Nitrogen found on earth’s crust occurs a s: Sodium nitrate(Chile saltpetre ) Potassium nitrate(Indian saltpetre ) Prosperous is found in minerals of apatite family. Also essential mineral for living organism.

5. Electronic Configuration   General electronic configuration ns2np3. Stability of +5 OS decreases as we move down the group due to inert pair effect .

6. Atomic Radii Nitrogen(N ) 70 Phosphorus(P) 110 Arsenic(As) 121 Antimony(Sb) 141 Bismuth(Bi ) 148 On moving down the group atomic radius is expected to increase .  As to Bi only a small increase in radius is observed due to ineffective shielding of filled d and/or f orbitals.

7. Ionization Enthalpy The ionization enthalpy values decreases down the group due to increase in size .  Group 15 elements have higher IE than group 14 and group16 due to stable half filled configuration.

8. Electronegativity   Down the group, electro negativity decreases. Nitrogen is most electronegative element of the group . Nitrogen forms Hydrogen bonds.

9. Physical Properties All the elements of this group are polyatomic. Except nitrogen, all the elements show allotropy and catenation. Exception: N is diatomic as N-N is weak due to interelectronic repulsion of lone pair . Metallic character increases down the group due to decrease in ionization enthalpy and increase in atomic size. N , P are non metals, As Sb metalloids and Bi metal. B.P. increases from top to bottom. M.P. increases up to arsenic and decreases for bismuth.

10. Oxidation State  Show Oxidation State  -3, +3 and +5  . tendency to exhibit –3 oxidation state decreases down the group due to increase in size and metallic character . The stability of +5 oxidation state decreases and • that of +3 state increases (due to inert pair effect) down the group. Bi only forms BiF5  . Nitrogen undergoes disproportion : 3HNO2 → HNO3 + H2O + 2NO

11. Anomal0us property of n Due to small size, high electronegativity, high IE and non availability of d orbitals N2 is unreactive (inert) due to strong p π – p π . Other elements of group do not form strong p π – p π as their atomic orbitals are large and diffuse so they cannot have effective overlapping . nitrogen cannot form d π – p π and d π – d π bond and maximum covalency of 4 : due to non availability of d orbitals Nitrogen cannot form R3P = O type compounds, or R3P = CH2 (R = alkyl group). Phosphorus , NCl5 not formed.

12. Reactivity Towards Hydrogen  H ydrides have formula EH3 • Bond dissociation enthalpy decreases down the group . Small size N overlaps better with H and overlap becomes less effective with increase in size of atom . The stability of hydrides decreases from NH3 to BiH3 due to decrease in bond dissociation enthalpy • T he reducing character of the hydrides increases down the group due to decrease in bond dissociation enthalpy . BiH3 is a strong reducing agent

13. Reactivity Towards Oxygen   Form oxides with formula E2O3 and E2O5  The oxide in the higher oxidation state of the element is more acidic than that of lower oxidation state A cidic character decreases down the group because metallic character increases  .

14. Reactivity Towards Halogens Form Halides with formula EX3 and EX5 . Nitrogen does not form pentahalide due to non- availability of the d orbitals in its valence shell . P entahalides are more covalent than trihalides. All the trihalides of these elements except those of nitrogen are stable. In case of nitrogen, only NF3 is known to be stable Trihalides except BiF3 are predominantly covalent in nature.

15. Reactivity Towards Metal All element react with metal to form binary compound. With -3 oxidisation state.