Oxygen and sulphur both are the member of same group in periodic table but `H_2O` is liquid while `H_2S` is gas because

Options

A. molecular weight of water is more
B. electronegativity of sulphur is more
C. `H_2S` is weak acid
D. water molecules are having strong hydrogen bonds between them

Answer

To understand why \( H_2O \) (water) is a liquid while \( H_2S \) (hydrogen sulfide) is a gas, we can analyze the properties of the molecules involved, particularly focusing on the concept of hydrogen bonding and electronegativity.

### Step-by-Step Solution:

1. **Identify the Elements and Their Group**:
- Oxygen (O) and sulfur (S) are both in Group 16 of the periodic table. This means they have similar valence electron configurations.

2. **Molecular Formulas**:
- The molecular formulas are \( H_2O \) for water and \( H_2S \) for hydrogen sulfide.

3. **Electronegativity Comparison**:
- Electronegativity is the ability of an atom to attract electrons in a bond. Oxygen is more electronegative (3.44 on the Pauling scale) than sulfur (2.58). This difference in electronegativity affects the polarity of the molecules.

4. **Polarity of Molecules**:
- In \( H_2O \), the oxygen atom pulls the shared electrons closer to itself, creating a polar molecule with a partial negative charge on the oxygen and partial positive charges on the hydrogens.
- In \( H_2S \), the difference in electronegativity is less pronounced, making the molecule less polar.

5. **Hydrogen Bonding**:
- The polarity of water allows for strong hydrogen bonding between water molecules. Each water molecule can form hydrogen bonds with up to four neighboring water molecules, resulting in a strong intermolecular attraction.
- In contrast, hydrogen sulfide does not exhibit significant hydrogen bonding due to its lower polarity. The intermolecular forces in \( H_2S \) are primarily van der Waals forces, which are much weaker.

6. **State of Matter at Room Temperature**:
- The strong hydrogen bonds in water keep the molecules closely packed, resulting in a liquid state at room temperature.
- The weaker intermolecular forces in \( H_2S \ allow the molecules to move freely, resulting in a gaseous state at room temperature. 7. **Conclusion**: - Therefore, the primary reason \( H_2O \) is a liquid while \( H_2S \) is a gas is due to the presence of strong hydrogen bonding in water, which is facilitated by the high electronegativity of oxygen compared to sulfur.

### Final Answer:
\( H_2O \) is a liquid while \( H_2S \) is a gas because water molecules form strong hydrogen bonds due to the high electronegativity of oxygen, whereas hydrogen sulfide does not form significant hydrogen bonds.