A nucleus represented by the symbol `._Z^AX` has.

Options

A. Z protons and A –Z neutrons
B. Z protons and A neutrons
C. A protons and Z –A neutrons
D. Z neutrons and A –Z protons

Explanation

To solve the question regarding the nucleus represented by the symbol \( _Z^A X \), we need to understand the meanings of the terms involved:

1. **Understanding the Symbols**:
- The symbol \( _Z^A X \) represents a nucleus where:
- \( A \) is the **mass number**.
- \( Z \) is the **atomic number**.
- \( X \) is the chemical symbol of the element.

2. **Definitions**:
- The **mass number (A)** is defined as the total number of protons and neutrons in the nucleus. This can be expressed as:
\[ A = \text{Number of Protons} + \text{Number of Neutrons} \]
- The **atomic number (Z)** is defined as the number of protons in the nucleus. Therefore, we can say:
\[ Z = \text{Number of Protons} \]

3. **Calculating Neutrons**:
- To find the number of neutrons in the nucleus, we can rearrange the mass number equation:
\[ \text{Number of Neutrons} = A - Z \]

4. **Conclusion**:
- From the definitions and calculations above, we can summarize:
- \( Z \) represents the number of protons.
- The number of neutrons can be calculated as \( A - Z \).

Now, let's check the options given in the question:

- **Option A**: \( Z \) is the number of protons, \( A - Z \) is the number of neutrons. (Correct)
- **Option B**: \( Z \) is the number of protons, \( A \) is the number of neutrons. (Incorrect)
- **Option C**: \( A \) is the number of protons. (Incorrect)
- **Option D**: \( Z \) is the number of neutrons. (Incorrect)

Thus, the correct option is **Option A**.