In which of the following arrangements the order is NOT according to the property indicated against it?

Which one of the following ions has the highest value of ionic radius?

Among Al₂O₃, SiO₂, P₂O₃ and SO₂ the correct order of acid strength is

The formation of the oxide ion O^2-(g) requires first an exothermic and then an endothermic step as shown below

O_(g) + e^- = $$O_{(g)}^{-}$$ $$\Delta $$H^o = -142 kJmol^-1

$$O_{(g)}^{-}$$ + e^- = $$O_{(g)}^{2-}$$ $$\Delta $$H^o = 844 kJmol^-1

This because