Question

Which of the following is a poor conductor of electricity?
A. Copper
B. Silver
C. Aluminium
D. Water

Answer 1

To solve this question, we should keep in mind the properties which classify a material as a conductor. In solid, materials which possess free electrons delocalised over its crystal structure conduct electricity. In liquids, ions are charge carriers and thus, its conductivity depends upon the dissociation of the compound into ions in a solution.

Complete step by step answer:
We know that a compound in solid state can conduct electricity only when it has free or unpaired electrons in its delocalised orbitals. These electrons travel throughout the crystal structure and thus, conducting electricity. In liquids, the compounds which easily dissociate into cations and anions can conduct electricity. The conductivity of such a solution depends upon its dissociation constant.
In option A, copper is a d-block transition element with electronic configuration: $_{29}Cu \to [Ar]3{d^{10}}4{s^1}$, which means that it has 1 unpaired electron in its valence shell and can thus conduct electricity.
In option B, silver is also a d-block element with electronic configuration: $_{47}Ag \to [Kr]4{d^{10}}5{s^1}$, which means it has an unpaired electron in its valence shell and can conduct electricity.
In option C, aluminium is a p-block element with electronic configuration: $_{13}Al \to [Ne]3{s^2}3{p^1}$ , we can see that it has an unpaired electron in its valence shell and can thus also conduct electricity.
In option D, water being a liquid, its conductivity depends upon is dissociation into ions, but due to the low concentration of ${H^ + }$ and $O{H^ - }$ ions, it is considered as a non-electrolyte and is a poor conductor of electricity.

$\therefore$ The correct option is option D, i.e. water .

Note:
In solids, metals are usually good conductors of electricity while non-metals are mostly insulators, except for graphite. The conductivity of metals decreases with an increase in temperature as higher temperature results in more vibration of ions which increase the resistivity of the metal and hence, decreases its conductivity. In liquids, acids, bases and salts are good conductors of electricity as they dissociate into ions very easily. They are also known as electrolytes. The conductivity of electrolytes decreases with increase in concentration, this is because at higher concentration mobility of ions decreases and thus, conductivity also decreases