Question

The following image is a cross section of a solid crystal of Iodine $({I_2})$. What type of crystal is represented by this iodine solid?

$(A)$ Ionic solid
$(B)$ Molecular solid
$(C)$ Covalent network solid
$(D)$ Nonmetal solid

Answer 1

Hint: Iodine is a nonmetallic, nearly black solid at room temperature and has a glittering crystalline appearance. The lattice contains discrete diatomic molecules, which are also present in the molten state and the gaseous state.

Complete Step By Step Answer:
Iodine crystal is into ionic type crystals because the given diagram is of simple cubic unit cells which are very orderly arranged i.e. iodine atoms at body corners.
Numerous unit cells together make a crystal lattice. Constituent’s particles like atoms, molecules are also present. Each lattice point is occupied by one such particle.
$ \bullet $ Primitive cubic unit cell
$ \bullet $ Body-centered unit cell
$ \bullet $ Face centered cubic unit cell
As the diagram shows the simple cubic unit cell or primitive cubic unit cell, we will only discuss primitive cubic unit cells. In the primitive cubic unit cell, the atoms are present only at the corners. Every atom at the corner is shared among eight adjacent unit cells. There are four unit cells in the same layer and four in the upper (or lower) layer. Therefore, a particular unit cell has the only $\dfrac{1}{{{8^{th}}}}$ of an atom. Each small sphere in the following figure represents the iodine particle that occupies that particular position and not its size. This structure is known as an open structure.
$ \bullet $ The atoms in the primitive cubic unit cells are present only at the corners
$ \bullet $ Every atom at the corner is shared among eight adjacent unit cells.
$ \bullet $ Four unit cells are present in same layer
$ \bullet $ Four unit cells in the upper layer.
$ \bullet $ Therefore, a particular unit cell has the only ${18^{th}}$ of an atom.
$ \bullet $ Each small sphere in the following figure represents the center of a particle which occupies that particular position and not its size.
Correct option is $(A)$; Ionic solid.

Note:
In each cubic unit cell, there are eight atoms at the type corner. Therefore the total number of atoms in one unit cell is $1$ atom. In body centered cubic unit cells there are $2$ atoms per unit cell and in face centered cubic unit cells there are $4$ atoms in a unit cell.