Classifying ZnS as an Ionic Crystal

Ionic crystals are a type of crystalline solid that is held together by ionic bonds. These bonds occur between positively and negatively charged ions. To determine whether ZnS is an ionic crystal or not, we need to consider the bonding between its constituent atoms.

Understanding the Bonding in ZnS

ZnS is composed of zinc (Zn) and sulfur (S) atoms. Zinc is a metal, while sulfur is a nonmetal. When these two elements combine, they form an ionic compound.

Formation of Ionic Bonds

Ionic bonds are formed when one atom loses electrons (becoming a positively charged ion) and another atom gains those electrons (becoming a negatively charged ion). In the case of ZnS, zinc loses two electrons to achieve a stable electron configuration like a noble gas, and sulfur gains these two electrons.

Formation of Zn2+ and S2- Ions

Zinc, with its atomic number of 30, has two electrons in its outermost shell. By losing these two electrons, it attains a stable electron configuration of argon (18 electrons). As a result, Zn forms a 2+ cation.

On the other hand, sulfur has six electrons in its outermost shell. By gaining two electrons, it completes its octet, attaining a stable electron configuration like neon (10 electrons). Thus, sulfur forms a 2- anion.

Formation of Zinc Sulfide (ZnS)

The electrostatic attraction between the positively charged zinc ions (Zn2+) and the negatively charged sulfide ions (S2-) creates the ionic bond in ZnS. This bond is strong and results in the formation of a three-dimensional lattice structure.

Characteristics of Ionic Crystals

Ionic crystals have several characteristic properties:

1. High melting and boiling points: Due to the strong ionic bonds, a large amount of energy is required to break the bonds and convert the solid crystal into a liquid or gas.

2. Brittle nature: The ionic lattice structure is easily disrupted by external forces, leading to the cleavage of the crystal.

3. Conductivity: In the solid state, ionic crystals do not conduct electricity. However, when melted or dissolved in water, the ions are free to move and conduct electricity.

4. Solubility: Ionic crystals are often soluble in polar solvents, as the polar molecules interact with the charged ions and help in their dissolution.

Based on the above characteristics and the nature of the bonding in ZnS, it can be concluded that ZnS is an ionic crystal.