Question

Discuss the diagonal relationship of Be and Al with regard to 

1. action of alkali

2. the structure of their chloride.

Answer 1

1. Be and Al both react with NaOH to form sodium beryllate and sodium meta aluminate respetively. Be dissolves in excess of NaOH to form [Be(OH)₄]² where as

Al forms [ Al(OH)₆]^3- in excess of NaOH.

2H₂O + Be + 2NaOH → Na₂ [Be(OH)₄] (saliun beryllali) + H₂

2Al + 6NaOH + 6H₂O → 2Na₃ [Al(OH)₆] (Sodium metal almunali) + 3H₂

2. BeCl₂ is electron deficient, therefore, has polymeric chain structure in solid state.

AlCl₃ is also electron deficient, It exists as dimmer, i.e., Al₂Cl₆