The stability of +1 oxidation state among Al, Ga, In and Tl increases in the sequence

Which of the statements given below is incorrect?

The formation of the oxide ion, O^2$$-$$_(g) from oxygen atom requires first an exthermic and then an endothermic step as shown below:
O_(g) + e^$$-$$ $$ \to $$ O^$$-$$_(g);  $$\Delta $$_fH^o = $$-$$141 kJ mol^$$-$$1

O^$$-$$_(g) + e^$$-$$ $$ \to $$ O^2$$-$$_(g);  $$\Delta $$_fH^o = +780 kJ mol^$$-$$1

Thus, process of formation of O^2$$-$$ is isoelectronic with neon. It is due to the fact that,

Nitrogen dioxide and sulphur dioxide have some properties in common . Which property is shown by one of these compounds , but not by the other?