The maximum covalency of Be and Mg respectively

Given, Maximum covalency of Be and Mg

Formula/concept used: Alkaline earth metal

Detailed solution: Be and Mg are the elements of alkaline earth metals. The alkaline earth metals are the elements of group 2 in the modern periodic table. General electronic configuration of group 2 elements are ${\mathrm{ns}}^2$. Covalency means the number of covalent bonds formed. Be can form maximum 4 covalent bonds. So, the covalency of Be is 4. Mg can form 6 covalent bonds, thus maximum covalency of mg is 6.

Therefore, option A is correct.