The trends in chemical reactivity of group 15 elements are given below:
(i) Reactivity with hydrogen: Group 15 elements form hydrides of the type EH3 where E is group 15 element. On moving down the group, the stability of hydrides decreases.
(ii) Reactivity with oxygen: Group 15 elements form the oxides E2O3 and E2O5. In the oxide, when the oxidation state of group 15 element is higher, it is more acidic than the one with lower oxidation state. On moving down the group, the acidic character decreases.
(iii) Reactivity with halogens : Group 15 elements form the salts EX3 and EX5. Nitrogen only forms NX3 but not NX5 as it lacks the d-orbital. NX3 is unstable and other trihalides are stable.
(iv) Reactivity towards metals: Group 15 elements form binary compounds with metals. In these compounds, the oxidation state of metal is -3.