The existence of nucleus was discovered by

Options

A. J.J. Thomson
B. Rutherford
C. Bohr
D. Pauli.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the discovery of the nucleus of an atom. We need to identify the scientist responsible for this discovery.

2. **Identifying the Scientist**: The nucleus was discovered by Ernest Rutherford. This is a key point in atomic theory.

3. **Rutherford's Experiment**: Rutherford conducted the famous gold foil experiment. In this experiment, he bombarded a thin gold foil with alpha particles (which are positively charged).

4. **Observations from the Experiment**:
- Most of the alpha particles passed straight through the gold foil without any deflection. This indicated that most of the atom is empty space.
- A small number of alpha particles were deflected at small angles, suggesting that there is a positive charge concentrated in a small area within the atom.
- A very few alpha particles (about 1 in 10,000) were deflected back at angles close to 180 degrees, indicating a very dense and positively charged center.

5. **Conclusion**: From these observations, Rutherford concluded that the nucleus is located at the center of the atom and contains most of its mass, composed of protons and neutrons. This led to the understanding that the nucleus is positively charged.

6. **Final Answer**: Therefore, the existence of the nucleus was discovered by Ernest Rutherford.

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