How many `109^(@)28'` bond angles in `CH_(4)` molecules?

Options

A. 2
B. 4
C. 6
D. 8

Answer

To determine how many bond angles of `109°28'` are present in a `CH₄` (methane) molecule, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Central Atom**:
The central atom in the `CH₄` molecule is carbon (C).

2. **Determine the Number of Bond Pairs and Lone Pairs**:
In `CH₄`, carbon forms four single bonds with four hydrogen atoms and has no lone pairs. Thus, there are 4 bond pairs and 0 lone pairs.

3. **Calculate the Steric Number**:
The steric number is calculated as the sum of bond pairs and lone pairs:
\[ \text{Steric Number} = \text{Number of Bond Pairs} + \text{Number of Lone Pairs} = 4 + 0 = 4 \]

4. **Determine Hybridization**:
A steric number of 4 corresponds to `sp³` hybridization.

5. **Identify the Molecular Geometry**:
The `sp³` hybridization results in a tetrahedral geometry for the molecule.

6. **Draw the Molecular Structure**:
When visualizing the structure of `CH₄`, you can see that the four hydrogen atoms are positioned at the corners of a tetrahedron with the carbon atom at the center.

7. **Identify the Bond Angles**:
In a tetrahedral geometry, the bond angles between the hydrogen atoms (H-C-H) are all equal to `109°28'`.

8. **Count the Number of Bond Angles**:
In the `CH₄` molecule, there are 6 unique bond angles formed between the hydrogen atoms:
- H1-H2
- H1-H3
- H1-H4
- H2-H3
- H2-H4
- H3-H4

Each of these angles measures `109°28'`.

### Final Answer:
Thus, the total number of `109°28'` bond angles in the `CH₄` molecule is **6**.

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