Which among the following is an element?

Options

A. Calcium oxide
B. Common salt
C. Ozone
D. Water

Answer

To determine which among the given options is an element, we need to understand the definitions of elements and compounds.

### Step-by-Step Solution:

1. **Understand the Definition of an Element**:
- An element is a pure substance that consists of only one type of atom.

2. **Identify the Options**:
- We have four options:
- A) Calcium Oxide (CaO)
- B) Common Salt (NaCl)
- C) Ozone (O3)
- D) Water (H2O)

3. **Analyze Each Option**:
- **Option A: Calcium Oxide (CaO)**
- This compound consists of one atom of calcium and one atom of oxygen. Since it is made from two different types of atoms, it is a compound, not an element.
- **Option B: Common Salt (NaCl)**
- Common salt is made up of one atom of sodium and one atom of chlorine. Like calcium oxide, it consists of two different types of atoms, making it a compound.
- **Option C: Ozone (O3)**
- Ozone consists of three atoms of oxygen. Since it is made from only one type of atom (oxygen), it qualifies as an element.
- **Option D: Water (H2O)**
- Water is composed of two hydrogen atoms and one oxygen atom. This combination of different types of atoms makes it a compound.

4. **Conclusion**:
- Among the given options, Ozone (O3) is the only substance that is an element. Therefore, the correct answer is **Option C: Ozone**.