Which of the following elements are oxidised when they react with dihydrogen?

Options

A. Calcium
B. Sulphur
C. Lithium
D. Carbon

Explanation

To determine which of the following elements are oxidized when they react with dihydrogen (H2), we need to analyze each element's reaction with H2 and identify if oxidation occurs.

### Step-by-Step Solution:

1. **Understanding Oxidation**:
- Oxidation is defined as the loss of electrons by an element. When an element reacts with dihydrogen, if it loses electrons, it is said to be oxidized.

2. **Identifying the Elements**:
- The elements provided in the question are:
- Calcium (Ca)
- Sulfur (S)
- Lithium (Li)
- Carbon (C)

3. **Analyzing Each Element's Reaction with Dihydrogen**:
- **Calcium (Ca)**:
- Calcium has 2 electrons in its outer shell. When it reacts with H2, it can lose these 2 electrons to form calcium hydride (CaH2).
- Reaction: \( \text{Ca} + \text{H}_2 \rightarrow \text{CaH}_2 \)
- Here, calcium is oxidized as it loses 2 electrons.

- **Sulfur (S)**:
- Sulfur typically gains electrons to form sulfide (S^2-). It does not lose electrons when reacting with H2.
- Reaction: \( \text{S} + \text{H}_2 \) does not lead to oxidation of sulfur.

- **Lithium (Li)**:
- Lithium has 1 electron in its outer shell. It can lose this 1 electron to form lithium hydride (LiH).
- Reaction: \( \text{Li} + \text{H}_2 \rightarrow \text{LiH} \)
- Here, lithium is oxidized as it loses 1 electron.

- **Carbon (C)**:
- Carbon can either gain or share electrons depending on its bonding. In the case of reacting with H2, it does not typically lose electrons to form a stable hydride.
- Reaction: \( \text{C} + \text{H}_2 \) does not lead to oxidation of carbon.

4. **Conclusion**:
- From the analysis, we find that calcium (Ca) and lithium (Li) are oxidized when they react with dihydrogen. Therefore, the elements that are oxidized are **Calcium (Ca) and Lithium (Li)**.

### Final Answer:
- The elements that are oxidized when they react with dihydrogen are **Calcium (Ca) and Lithium (Li)**.