Question

Solid $C{O}_2$ is an example of:
A. Ionic crystal
B. Covalent crystal
C. Metallic crystal
D. Molecular crystal

Answer 1

Hint- In order to solve this question, we must know the concept of solids and its classification. Then we will broadly study the four types of atomic bonds which are found in crystalline solids to get the required result.

Complete answer:
Firstly, we must know the concept of solids.
Solid is one of the basic three states of matter, the other being liquid and gas. Solids exhibit certain characteristics that distinguish them from liquids and gases. Solids are divided into three broad classes-
1. Crystalline
2. Non-crystalline
3. Quasi-crystalline
Crystalline solids have a very high degree of order in a periodic atomic arrangement. Practically all metals and many other minerals, such as common table salt belong to this class.
Non-crystalline solids are those in which atoms and molecules are not organized in a definite lattice pattern. They include glasses, plastics and gels.
Quasi-crystalline structures display novel symmetries in which the atoms are arranged in quasi-periodic fashion. These structures are common in alloys in which aluminum is combined with another metal such as cobalt, nickel.
Now as the question is particularly about crystals, so we will see the four types of atomic bonds which are found in crystalline solids-
1. Metallic crystals
2. Ionic crystals
3. Covalent crystals
4. Molecular crystals
$\Rightarrow$ Metallic crystals-
Metals and their alloys are characterized in the main by their high electrical and thermal conductivity which arises from migration of free electrons, free electrons also influence how the atoms bond.
$\Rightarrow$ Ionic crystals-
Ionic crystals are aggregates of charged ions. These salts commonly exhibit ionic conductivity, which increases with temperature.
$\Rightarrow$ Covalent crystals-
Covalent crystals are hard, frequently brittle materials such as diamond, silicon and silicon carbide. In the simpler monatomic types, each atom is surrounded by a number of atoms equal to its valence.
$\Rightarrow$ Molecular crystals-
Molecular crystals are substances that have relatively weak intermolecular binding, such as dry ice (solidified carbon dioxide), solid forms of the noble gases (e.g. argon, krypton, xenon).
Therefore from all the four types of atomic bonds found in crystalline solids-
We conclude that Solid $C{O}_2$is an example of molecular crystals.

Hence, option D is correct.

Note- While solving this question, we should know all the four types of atomic bonds found in crystalline solids so that we get the appropriate answer. Also one must know the classification and properties of crystals to solve similar kinds of questions.