When does the nucleus of an atom tend to be radioactive ?

Explanation

**Step-by-Step Text Solution:**

1. **Understanding the Nucleus**: The nucleus of an atom is composed of protons and neutrons. Protons are positively charged, while neutrons have no charge.

2. **Balance of Protons and Neutrons**: In a stable nucleus, there is a balanced ratio of protons to neutrons. This balance is crucial for the stability of the nucleus.

3. **Radioactive Nuclei**: A nucleus tends to be radioactive when it is unstable. This instability often arises when there is an imbalance in the number of protons and neutrons.

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