Give reasons -
K atom is bigger than Na atom even though both these elements belong to same group.
The metallic character of elements increases as we move down a group.
Mg atom is smaller than Na even though these elements belong to same period.

Explanation

### Step-by-Step Solution:

1. **Potassium Atom Size Compared to Sodium Atom:**
- **Reason:** Potassium (K) is larger than Sodium (Na) because they belong to the same group (Group 1), but potassium is in the fourth period while sodium is in the third period. As you move down a group in the periodic table, the number of electron shells increases. Potassium has one more electron shell than sodium, which results in a larger atomic radius.
- **Conclusion:** Thus, K atom is bigger than Na atom due to the increase in the number of electron shells.

2. **Metallic Character Increases Down a Group:**
- **Reason:** The metallic character of elements increases as you move down a group because the atomic size increases. As the size of the atom increases, the outermost electrons are farther from the nucleus. This results in a decrease in the effective nuclear charge felt by the outermost electrons, making it easier for these electrons to be lost. Therefore, elements become more electropositive and exhibit stronger metallic character as you go down a group.
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