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

The correct order of bond angles (smallest first) in H₂S, NH₃, BF₃ and SiH₄ is

The bond order in NO is 2.5 while that in NO⁺ is 3. Which of the following statements is true for these two species?

The states of hybridization of boron and oxygen atoms in boric acid (H₃BO₃) are respectively