Which of these is an elements?

Options

A. Iron
B. Water
C. Carbon dioxide
D. Sodium chloride

Answer

**Step-by-Step Solution:**

1. **Understanding the Definition of an Element:**
- An element is a pure substance that consists of only one type of atom. It cannot be broken down into simpler substances by chemical means.

2. **Analyzing the Options:**
- We have four options to evaluate: iron, water, carbon dioxide, and sodium chloride.

3. **Evaluating Option 1: Iron**
- Iron (Fe) is a substance that consists solely of iron atoms. Therefore, it qualifies as an element.

4. **Evaluating Option 2: Water**
- Water (H2O) is made up of two hydrogen atoms and one oxygen atom. Since it contains more than one type of atom, it is not an element; it is a compound.

5. **Evaluating Option 3: Carbon Dioxide**
- Carbon dioxide (CO2) consists of one carbon atom and two oxygen atoms. Like water, it contains more than one type of atom, thus it is also a compound and not an element.

6. **Evaluating Option 4: Sodium Chloride**
- Sodium chloride (NaCl) is composed of one sodium atom and one chlorine atom. Since it has two different types of atoms, it is a compound and not an element.

7. **Conclusion:**
- After evaluating all options, the only substance that qualifies as an element is iron (Option 1).

**Final Answer:**
- The correct answer is **Option 1: Iron**.

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