Question

Which type of solid crystals will conduct heat and electricity?
(a) Ionic crystals
(b) Covalent crystal
(c) Metallic crystals
(d) Molecular crystals

Answer 1

Hint: The solid crystals which having free movable electrons have the tendency to conduct heat and electricity. Such crystals have excess free electrons.

Complete Step by Step Solution:
The ionic crystal, covalent crystal, and molecular crystal do not possess free movable valence electrons. Hence, they cannot conduct heat and electricity.
The solid in which the atoms are connected by mean of metallic bonds are called a metallic solid. The metals, alloy, and interstitial solids are the best examples of metallic solids.
In metallic solids, the positively charged metal ions (Kernels) are surrounded by a sea of movable valence electrons. Each positively charged metal ion is surrounded by several electrons and vice versa.
The force which binds positively charged metal ions to a number of electrons is known as a metallic bond. This strong force of attraction is the reason for the compactness of metallic solids.
Metallic solids have high melting and boiling point due to the presence of strong metallic bonds.
Metallic solids are malleable and can be converted into a thin film.
Metallic solids are good conductors of heat and electricity due to the presence of mobile valence electrons. The copper\[Cu\], silver\[Ag\], gold\[Au\], \[Ni\],etc. are examples of metallic solids.
Hence, metallic crystals are the best candidate to conduct heat and electricity, option (c) will be the correct answer.

Note: In the ionic crystal, the ions are bonded to each other by a strong force of attraction hence they cannot conduct heat and electricity. Similarly, in covalent and molecular crystals the electrons are also busy in making bonding. Hence, they also cannot conduct heat and electricity.