Acidic nature : H2O < H2S < H2Se < H2Te
This is because the H-E bond length increases down the group . Therefore , the bond dissociation enthalpy decreases down the group .
Thermal stability : H2O < H2S < H2Se < H2Te < H2Po
This is because the H-E bond length increases down the group . Therefore , the bond dissociation enthalpy decreases down the group .
Reducing character : H2O < H2S < H2Se < H2Te < H2P
This is because the H-E bond length increases down the group . Therefore , the bond dissociation enthalpy decreases down the group .
30 . Reactivity with oxygen : EO2 and EO3
Reducing character of dioxides decreases down the group because oxygen has a strong positive field which attracts the hydroxyl group and removal of H + becomes easy .
Acidity also decreases down the group .
SO2 is a gas whereas SeO2 is solid . This is because SeO2 has a chain polymeric structure whereas SO2 forms discrete units .