Why does the size of the atom increase down the group?

Explanation

To understand why the size of an atom increases down a group in the periodic table, we can break down the explanation into several key steps:

### Step-by-Step Solution:

1. **Understanding Atomic Number**:
- The atomic number of an element is defined as the number of protons in its nucleus. In a neutral atom, this is also equal to the number of electrons.

**Hint**: Remember that the atomic number is crucial in determining the properties of an element.
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