. Discuss the trends in chemical reactivity of group 15 elements
Trends in chemical reactivity of group 15 elements.
1. Oxidation State : Same as in Question 1.
2. Reactivity Towards Hydrogen : These elements form covalent hydrides with the formula EH3. [where, E = N, P, As Sb]
(a) Thermal stability of hydrides decreases down the group.
(b) Reducing character of hydrides increases down the group.
(c) Basic character of hydrides decreases down the group.
(d) Boiling point of NH3 is greater than PH3 due to H-bonding.
Boiling points of other hydrides increase from PH3 onwards.
Lighter elements like nitrogen also form hydrides of the formula E2H4. .e.g, N2H4
3. Reactivity towards halogens : All group 15 elements i.e., N, P, As, Sb,Bi form
(a) Halides of general formula EX3. Except NBr3 and NI3, all are stable with pyramidal shape, These get hydrolyzed by water.
(b) Halides of general formula EX5. These are formed by P, As and Sb but not by N. These halides are trigonal bipyramidal with sp3d hybridization.
4. Reactivity towards oxygen. These elements form oxides of the formula E2O3 and E2O5. However, nitrogen because of its tendency to form pp -pp multiple bonds, form a range of oxides having oxidation states +1 to +5 (e.g., N2O, NO, N2O3, NO2, N2O4, N2O5) E2O5 are more acidic than E2O3. Acidic character of oxides decreases down the group.