Why do you think the noble gases are placed in a separate group?

Explanation

### Step-by-Step Solution

1. **Understanding Noble Gases**: Noble gases are a group of elements that include helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe). They are located in Group 18 of the periodic table, which is also referred to as the zero group.

2. **Electron Configuration**: The defining characteristic of noble gases is their electron configuration. They have completely filled outer electron shells. For example:
- Helium: 1s²
- Neon: 1s² 2s² 2p⁶
- Argon: 1s² 2s² 2p⁶ 3s² 3p⁶
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