Be shows diagonal relationship with Al. Disicuss.

Explanation

Be shows diagonal relationship with Al
The ionic radius of `Be^(+2)` is nearly same as that of `Al^(+3)` so Be resembles AL in several ways.
Al , be both not readily reacts with acids . This is due to the presence of an oxide film on the surface of metal.
`Al(OH)_3,Be(OH)_2` both similarly dissolves in excess of alkali and forms Beryllate ion `[Be(OH)_3]^(2-)` and Aluminate `[Al(OH)_4]` ions respectively.
THe chlorides of Be, Al have bridged chloride structures in vapour phase.
Both the chlorides of Be, Al used as strong Lewis acid.
Both the chlorides of Be, AL used in Friedal craft catalysts.
Be, AL ions have strong tendency to form complexes.