Question

The maximum covalency of aluminium is-
(A) 4
(B) 6
(C) 8
(D) 3

Answer 1

The covalency of the element is determined by the number of electrons shared while forming a chemical compound. The covalency can easily be determined by knowing the electronic configuration of the element.

Complete answer:
Let us study about the given element in detail-
Aluminium-
Aluminium is the element with atomic number 13. Thus, the electronic configuration is $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{1}}$ . The element has free d-orbitals in the form of 3d-orbitals.
It is the property of p-block elements to expand their covalency from third period onwards due to availability of d-orbitals. Thus, the elements with empty d-orbitals can form compounds with higher covalency; generally.
Here, we can see that the element has 1 electron in the p-orbital. The rest two p-orbitals and five d-orbitals are free from electrons. Thus, the maximum covalency can be calculated as;
$Covalency=1+2+5=8$
But aluminium is the small ion and it is hard for the element to accommodate 8 electrons as it causes instability in the compound. With some reagents, aluminium shows 3 or 4 or 6 as its covalency.
But considering overall a point, we can say that the maximum covalency of aluminium is 8.

Therefore, option (C) is correct.

Note:
Do note that the term valency and covalency are different. Covalency is the actual number of electrons taking part in the covalent bond formation whereas, valency is the required number of electrons to complete the octet of an element.