Chemical reactivity of group 15 elements towards hydrogen, oxygen, halogens, and metals are discussed below.

(i) Reactivity towards hydrogen: Group 15 elements react with H to form hydrides of type EH₃ where E=N, P, As, Sb or Bi. On moving down from NH₃ to BiH₃, the stability of the hydrides decreases. For example, the P-H bond in PH₃ is less stable than the N-H bond in NH₃. The strength of the E-H bond gets weaker as the size of the central atom increases.

Stability order of E-H bond (where E is group 15 elements) can be represented as

N-H > P-H > As-H > Sb-H > Bi-H

(ii) Reactivity towards oxygen: Group 15 elements react with O to form oxides of the type E₂O₃ and E₂O₅ where E = N, P, As, Sb or Bi. The oxide of the element with higher oxidation state is more acidic than those with lower oxidation states. Down the group, the acidic character of the oxides decreases.

(iii) Reactivity towards halogens: Group 15 elements form halides of the type EX₃ and EX₅ where E = N, P, As, Sb or Bi. However, N does not form pentahalides EX₅ as it lacks d-orbital. All group 15 elements form trihalides but trihalides of N are unstable.

(iv) Reactivity towards metals: Group 15 elements react with metals to form compounds of general formula M₃E₂ where E= N, P, As, Sb or Bi. The binary compounds formed by the reaction of group 15 elements with metal show oxidation state -3.