Zinc oxide is found in ointments for the skin. What formula best describes this compound, which has Zn as a doubly charged cation? ZnO₂ Zn₃O₂ ZnO ZnO ZnO
The Correct Answer and Explanation is:
The correct formula for zinc oxide is ZnO.
Explanation:
Zinc oxide is an ionic compound composed of zinc (Zn) and oxygen (O). To determine its chemical formula, we must consider the charges of the ions involved and ensure that the overall compound is electrically neutral.
1. Zinc Ion (Zn²⁺):
Zinc is a metal found in Group 12 of the periodic table. It forms a stable Zn²⁺ ion by losing two electrons. This is a doubly charged cation (+2 charge), and it always has this oxidation state in ionic compounds.
2. Oxide Ion (O²⁻):
Oxygen is a nonmetal and commonly forms the oxide ion (O²⁻) when it gains two electrons. This is a doubly charged anion (−2 charge).
3. Combining Ions:
To form a neutral compound, the total positive charge must balance the total negative charge. Since Zn²⁺ and O²⁻ both carry equal but opposite charges, one ion of each is needed:
- Zn²⁺ + O²⁻ → ZnO
Thus, the formula ZnO correctly represents zinc oxide, with the +2 charge from zinc balanced by the −2 charge from oxygen.
4. Common Uses and Properties:
Zinc oxide is a white, powdery substance that is insoluble in water but widely used in various products. It is a common ingredient in skin ointments, sunscreens, and diaper rash creams because it acts as a skin protectant and has antibacterial and anti-inflammatory properties. ZnO also reflects ultraviolet (UV) light, making it useful in sun protection.
In addition to medical uses, ZnO is used in rubber manufacturing, ceramics, and as a pigment in paints. Its versatility comes from its stability, non-toxicity, and ability to block harmful radiation.
Conclusion:
The formula for zinc oxide is ZnO, representing a 1:1 ratio of Zn²⁺ to O²⁻, forming a neutral ionic compound.
