Beryllium salts can never have more than 4 molecules of water of crystallisation, i.e., it can never achieve coordination number > 4 while other metal ions tend to have a coordination number of 6, e.g., `[Ca(H_2O)_6]^(2+)`. Explain.

Explanation

Beryllium does not exhibit coordination number more than 4 because in its valence shell of Be^(2+)` ion there are only four available orbitals (one s and three p) present. The remaining members of the group can have a coordination number of six by using their d -orbitals along with s -and p -orbitals.