Question

p-Block elements form acidic, basic and amphoteric oxides. Explain each property by giving two examples and also write the reactions of these oxides with water.

Answer 1

In p-block, when we move from left to right in a period, the acidic character of the oxides increases due to increase in electronegativity. For example,  

In 2^nd period B₂0₃ < C0₂ < N₂0₃ (acidic nature increases). 

In 3^rd period A1₂0₃ < Si0₂ < P₄O₁₀ < S0₃ < Cl₂0₇ (acidic character increases). 

On moving down the group, acidic character decreases and basic character increases, e.g.,

Among the oxides of same element, higher the oxidation state of the element, stronger is the acid. For example, S0₃ is a stronger acid than S0₂. B₂0₃ is weakly acidic and on dissolution in water, it forms orthoboric acid. Orthoboric acid does not act as a protonic acid (it does not ionise) but acts as a weak Lewis acid.