In an atom with atomic no. 25 and mass no. 55,the number of electron is:

Options

A. 25
B. 55
C. 30
D. 35

Explanation

To find the number of electrons in an atom with atomic number 25 and mass number 55, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Atomic Number**: The atomic number (Z) is given as 25. The atomic number represents the number of protons in the nucleus of the atom.

2. **Understand the Relationship Between Protons and Electrons**: In a neutral atom, the number of protons is equal to the number of electrons. This means that if we know the atomic number, we can directly determine the number of electrons.

3. **Determine the Number of Electrons**: Since the atomic number is 25, the number of protons is also 25. Therefore, the number of electrons in this neutral atom is also 25.

4. **Conclusion**: The number of electrons in the atom with atomic number 25 is 25.

### Final Answer:
The number of electrons in the atom is **25**.

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