2. Определите валентность по формулам: Cl2O5, SO3, Fe2S3, NO2, HBr, BaO, SiH4, CuO, ZnCl2.

1. Cl2O5 (Cl-V, O-II), SO3 (S-VI, O-II), Fe2S3 (Fe-III, S-II), NO2 (N-IV, O-II), HBr (H-I, Br-I), BaO (Ba-II, O-II), SiH4 (Si-IV, H-I), CuO (Cu-II, O-II), ZnCl2 (Zn-II, Cl-I).