Question

Boron is an example of,
A. Metal
B. Non-Metal
C. Metalloid
D. Alloy

Answer 1

Hint: We know that metalloids are such elements which exhibit the property of both metals and nonmetals. Examples of metalloids are; silicon, boron, antimony, etc.

Complete answer
Silicon is lustrous like metal, whereas brittle like non-metal. Also, the electrical conductivity of metalloid lies in between the metals and non-metals. Alloys are described as a homogeneous mixture of a metal with a metal or a non-metal.
The electronic configuration of boron is ${\rm{1}}{{\rm{s}}^{\rm{2}}}{\rm{,}}\;{\rm{2}}{{\rm{s}}^{\rm{2}}}{\rm{,}}\;{\rm{2}}{{\rm{p}}^{\rm{1}}}$. Since, the outermost shell contains only 3 electrons, it has the need of 3 more electrons to obtain its inert gas configuration. So, in order to complete its octet, the boron forms a covalent bond. Covalent bond is formed by sharing electrons. Boron atoms form covalent bonds by sharing the valence electrons.
Boron is electron deficient and has vacant p-orbitals. It is also the one and only one non-metal group thirteen. Boron can also react with highly electronegative elements like fluorine in the same way a metal reacts and it can also react with a highly electropositive element like sodium in the same way as a nonmetal reacts. We also know that the boron hydrides are covalent in nature like methane and phosphine. And the fluoride of boron boron trifluoride and hydride of boron i.e. borane is hard acid and soft acid in nature respectively.
Their properties lie in between metal and non-metal, for example it does not conduct electricity. Also, some of its properties are similar to carbon and silicon.
So, we can say that the physical and chemical properties of boron are in between metal and nonmetal so it is a metalloid.

Hence option (C) Metalloid, is the correct option.

Note
The crystal boron is dark in colour and very hard like that of diamond. The other examples of metalloid include silicon, germanium, arsenic, antimony and tellurium.