If the mass number of an element is W and its atomic number is N, then

Options

A. number of `""_(-1)^(0)e=W-N`
B. number of `""_(1)^(1)H=W-N`
C. number of `""_(0)^(1)e=W-N`
D. number of `""_(0)^(1)n=N`

Answer

To solve the question, we need to understand the relationship between mass number (W), atomic number (N), and the number of neutrons in an atom.

### Step-by-Step Solution:

1. **Understand Key Definitions**:
- **Mass Number (W)**: The total number of protons and neutrons in the nucleus of an atom.
- **Atomic Number (N)**: The number of protons in the nucleus of an atom.

2. **Establish the Relationship**:
- The relationship between mass number (W), atomic number (N), and the number of neutrons (Neutrons) can be expressed with the formula:
\[ \text{Mass Number} (W) = \text{Atomic Number} (N) + \text{Number of Neutrons} \]

3. **Rearranging the Formula**:
- To find the number of neutrons, we can rearrange the formula:
\[ \text{Number of Neutrons} = W - N \]

4. **Conclusion**:
- Therefore, if the mass number of an element is W and its atomic number is N, the number of neutrons in that element is given by:
\[ \text{Number of Neutrons} = W - N \]

5. **Select the Correct Option**:
- Based on the options provided in the question, the correct option is:
- Option 1: The number of neutrons is equal to \( W - N \).
- Option 3: The number of neutrons is equal to \( W - N \) (this option is repeated).
- Both options 1 and 3 are correct, but since the question asks for one, we can state that the answer is option 1.

### Final Answer:
The number of neutrons in the element is \( W - N \).

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