Question

A solid that is not transparent to visible light and whose electrical conductivity increases with temperature is formed by:
A.Ionic bonding
B.Covalent bonding
C.Metallic bonding
D.Van der Waals’ bonding

Answer 1

To solve this question, we must individually discuss the different types of bonds that are mentioned in the options. Then we must understand the properties and characteristics of these bonds in order draw conclusions for obtaining the final answer

Complete Step-by-Step Answer:
Before we move forward with the solution of the given question, let us first understand some important basic concepts.
1.Ionic bonding: Ionic bonds are formed by the direct sharing of electrons between two or more atoms. When the electronegativity difference between the bonding atoms is significant enough, the more electronegative atom tends to attract valence electrons from the less electronegative atom. These bonds form free electrons which are very useful in the conduction of electricity.
2.Covalent bonding: Covalent bonds are formed by the sharing of electrons between two chemical species. These bonds do not result in the formation of ions or free electrons
3.Metallic bonding: Metallic bonds can be understood as those special bonds that are formed only between metals because of their freely flowing electrons. Metals are highly electropositive in nature. Because of this, there are always free flowing electrons in the lattice of a metal compound. These electrons act like glue and give the substance a definite structure.
4.Van der Waals’ bonding: Van der Waals’ bonds are formed in polar compounds because of the fluctuations in the polarization of these molecules.
Now, usually semiconductors are usually the compounds which are solid substances, transparent to light and also show an increase in their conductivity with the increase in temperature. This particular property is known as a positive temperature coefficient.

Hence, Option B is the correct option

Note: Semiconductors are materials which have a conductivity between conductors (generally metals) and non - conductors or insulators (such as most ceramics). Semiconductors usually form covalent bonds in their lattices.