Question

Beryllium and aluminium exhibit many properties which are similar. But the two elements differ in:
A) Maximum covalency in compounds.
B) Exhibiting amphoteric nature in their oxides.
C) Forming covalent halides.
D) Forming polymeric hydrides.

Answer 1

The covalency of Beryllium and aluminum is different due to differences in their atomic number and their electronic configuration. Be belongs to period number second and Aluminium belongs to period number 3.

Complete answer:
Beryllium and aluminium exhibit a diagonal relationship, in the periodic table. Two elements exhibit a diagonal relationship when these elements exist diagonally adjacent to the position in the periodic table. The diagonal relationship is generally seen in the second and third group of periodic tables.
Be and Al exhibit almost similar properties due to their diagonal position. Both the elements have the tendency to form covalent bonds and have the same electronegative charge on it. Both the elements even act as Lewis acids in which they can behave either as acid or base when reacting with certain compounds. On reaction both the elements can even form polymeric structure.
But due to the difference in their atomic number and electronic configuration their covalency varies.
Element Be has covalency 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. Both elements have the tendency to form covalent compounds.
Hence they differ in exhibiting the maximum covalency in compounds.

Therefore the correct option is option(A).

Note: Both the elements form covalent bonds and due to their high covalent nature their electrons get shared and they form tetrahedral or octahedral structure.