Isotopes are the atoms of same element having........ mass number and ................atomic number.

Answer

To solve the question regarding isotopes, we need to understand the definitions of mass number and atomic number, as well as the characteristics of isotopes.

### 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. **Defining Atomic Number**:
- The atomic number (Z) of an element is the number of protons in the nucleus of an atom. Since isotopes are atoms of the same element, they must have the same atomic number.

3. **Defining Mass Number**:
- The mass number (A) of an atom is the total number of protons and neutrons in the nucleus. Isotopes differ in their mass number because they have different numbers of neutrons.

4. **Filling in the Blanks**:
- Based on the definitions:
- Isotopes are the atoms of the same element having **different mass number** and **same atomic number**.

### Final Answer:
Isotopes are the atoms of the same element having **different mass number** and **same atomic number**.

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