Question

What is a nonmetal in group $13$?

Answer 1

The group $13$ contains six elements. They are boron, aluminium, gallium, indium, thallium and nihonium. Group $13$ is called the boron family. All the elements of this group have three electrons in their external shell of their nuclear structure.

Complete answer:
The non-metal that is present in the boron family is boron. This element has both metallic and non-metallic properties. It is classified as a metalloid. A metalloid is an element which has properties that are intermediate between those of nonmetals and metals. Metalloids can also be semimetals. Boron is electron deficient with a vacant p-orbital and usually tends to form both bases and acids. It is the lightest of all the elements present in group $13$. The element aluminium of the boron family is amphoteric in nature. That means it has reactions as both an acid and a base. Boron behaves as a nonmetal whereas all other elements show metallic characteristics. This is due to the growth in effective nuclear charge in the boron family. This arises due to the weak protection from the atomic charge by the occupied $(n - 1){d^{10}}$ and $(n - 2){f^{14}}$ subshells.
Therefore, the non-metal in group $13$ is boron.

Note:
Note that the element boron has a high melting point due to its small size. As it is small in size, it forms strong covalent bonds with adjacent atoms, so boron atoms have a close packing structure in solid state. Hence, a large amount of heat is needed to break the bonds between the boron atoms.