Explain the anomalous behavior of beryllium.

(N/A) Beryllium,the first member of the Group-$2$ metals,shows anomalous behavior compared to magnesium and the rest of the members. It also shows a diagonal relationship with aluminium.
$(i)$ Beryllium has an exceptionally small atomic and ionic size,which makes it distinct from other members of the group. Due to its high ionisation enthalpy and small size,it forms compounds that are largely covalent and easily hydrolysed.
$(ii)$ Beryllium does not exhibit a coordination number greater than four because its valence shell contains only four orbitals. Other members of the group can achieve a coordination number of six by utilizing $d$-orbitals.
$(iii)$ The oxide and hydroxide of beryllium are amphoteric in nature,unlike the hydroxides of other elements in the group,which are basic.