Isotopes of an element differ in the number of ………in their nuclei

Explanation

To answer the question "Isotopes of an element differ in the number of ……… in their nuclei," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Isotopes**:
- Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. This means they have the same atomic number but different mass numbers.

2. **Identifying Key Particles in the Nucleus**:
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