The number of valency electrons and the velency with respect to hydrogen are equal for

Options

A. Sulphur
B. Silicon
C. Phosphorus
D. Chlorine

Explanation

To solve the question regarding the equality of the number of valence electrons and valency with respect to hydrogen, we will analyze the valence electrons and the valency of different elements.

### Step-by-Step Solution:

1. **Identify the Elements**: We need to consider elements from different groups of the periodic table and their respective hydrides. The elements we will analyze include Sulfur (S), Silicon (Si), Phosphorus (P), and Chlorine (Cl).

2. **Determine Valence Electrons**:
- **Sulfur (S)**: Group 16, has 6 valence electrons.
- **Silicon (Si)**: Group 14, has 4 valence electrons.
- **Phosphorus (P)**: Group 15, has 5 valence electrons.
- **Chlorine (Cl)**: Group 17, has 7 valence electrons.

3. **Determine Valency with Respect to Hydrogen**:
- **Sulfur (S)**: Forms H₂S (Hydrogen Sulfide), valency = 2.
- **Silicon (Si)**: Forms SiH₄ (Silane), valency = 4.
- **Phosphorus (P)**: Forms PH₃ (Phosphine), valency = 3.
- **Chlorine (Cl)**: Forms HCl (Hydrogen Chloride), valency = 1.

4. **Compare Valence Electrons and Valency**:
- **Sulfur**: 6 valence electrons, valency = 2 (not equal).
- **Silicon**: 4 valence electrons, valency = 4 (equal).
- **Phosphorus**: 5 valence electrons, valency = 3 (not equal).
- **Chlorine**: 7 valence electrons, valency = 1 (not equal).

5. **Conclusion**: The only element for which the number of valence electrons is equal to the valency with respect to hydrogen is Silicon (Si).

### Final Answer:
The number of valence electrons and the valency with respect to hydrogen are equal for **Silicon (Si)**.