The correct order of bond angles in the molecules, `H_2O`, `NH_3`, `CH_4`, and `CO_2` is

Options

A. `H_2O gt NH_3 gt CH_4 gt CO_2`
B. `H_2O lt NH_3 lt CO_2 lt CH_4`
C. `H_2O lt NH_3 gt CO_2 gt CH_4`
D. `CO_2 gt CH_4 gt NH_3 gt H_2O`

Explanation

To determine the correct order of bond angles in the molecules H₂O, NH₃, CH₄, and CO₂, we will analyze the molecular geometry and the bond angles associated with each molecule step by step.

### Step 1: Analyze H₂O (Water)
- **Central Atom**: Oxygen (O)
- **Valence Electrons**: Oxygen has 6 valence electrons.
- **Bonds**: It forms 2 single covalent bonds with 2 hydrogen atoms, using 2 of its valence electrons.
- **Lone Pairs**: This leaves 4 valence electrons, which form 2 lone pairs.
- **Steric Number**: The steric number is calculated as the number of bonded atoms (2) plus the number of lone pairs (2), giving a steric number of 4.
- **Geometry**: The molecular geometry is tetrahedral, but the shape is bent or angular due to the presence of lone pairs.
- **Bond Angle**: The bond angle in H₂O is approximately 104.5°.

### Step 2: Analyze NH₃ (Ammonia)
- **Central Atom**: Nitrogen (N)
- **Valence Electrons**: Nitrogen has 5 valence electrons.
- **Bonds**: It forms 3 single covalent bonds with 3 hydrogen atoms, using 3 of its valence electrons.
- **Lone Pairs**: This leaves 2 valence electrons, which form 1 lone pair.
- **Steric Number**: The steric number is 3 (bonded atoms) + 1 (lone pair) = 4.
- **Geometry**: The molecular geometry is tetrahedral, and the shape is trigonal pyramidal.
- **Bond Angle**: The bond angle in NH₃ is approximately 107°.

### Step 3: Analyze CH₄ (Methane)
- **Central Atom**: Carbon (C)
- **Valence Electrons**: Carbon has 4 valence electrons.
- **Bonds**: It forms 4 single covalent bonds with 4 hydrogen atoms, using all of its valence electrons.
- **Lone Pairs**: There are no lone pairs.
- **Steric Number**: The steric number is 4 (bonded atoms) + 0 (lone pairs) = 4.
- **Geometry**: The geometry is tetrahedral.
- **Bond Angle**: The bond angle in CH₄ is 109.5°.

### Step 4: Analyze CO₂ (Carbon Dioxide)
- **Central Atom**: Carbon (C)
- **Valence Electrons**: Carbon has 4 valence electrons.
- **Bonds**: It forms 2 double bonds with 2 oxygen atoms, using all of its valence electrons.
- **Lone Pairs**: There are no lone pairs.
- **Steric Number**: The steric number is 2 (bonded atoms) + 0 (lone pairs) = 2.
- **Geometry**: The geometry is linear.
- **Bond Angle**: The bond angle in CO₂ is 180°.

### Step 5: Arrange the Bond Angles
Now that we have the bond angles for each molecule:
- H₂O: 104.5°
- NH₃: 107°
- CH₄: 109.5°
- CO₂: 180°

### Final Order of Bond Angles
The correct order of bond angles from smallest to largest is:
1. H₂O: 104.5°
2. NH₃: 107°
3. CH₄: 109.5°
4. CO₂: 180°

Thus, the final answer is:
**H₂O < NH₃ < CH₄ < CO₂**