# Beryllium and aluminium exhibit many properties which are similar. But, the two elements differ in Option 1) exhibiting maximum covalency in compounds Option 2) forming polymeric hydrides Option 3) forming covalent halides Option 4) exhibiting amphoteric nature in their oxides.

S Sabhrant Ambastha

As we learnt in

Diagonal relationship -

Similarity in properties between first element of a group and second element of the next group

- wherein

This is due to similarity in sizes of their ions, and charge / radius ratio

and

Anomalous behavious beryllium -

1) Due to small atomic and ionic size

2) High ionisation energy

3) No vacant d-orbitals

4) High hydration energy

-

Due to diagonal relationship  $Be$ and $Al$ exhibit many similar properties but covalency of $Be$ is 4 because it has an absence of d-orbital whereas, covalency of $Al$ is up to 6 due to the presence of vacant d-orbital.

Option 1)

exhibiting maximum covalency in compounds

This option is correct.

Option 2)

forming polymeric hydrides

This option is incorrect.

Option 3)

forming covalent halides

This option is incorrect.

Option 4)

exhibiting amphoteric nature in their oxides.

This option is incorrect.

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