Which of the following is a noble gas ?

Options

A. Hydrogen
B. Helium
C. Oxygen
D. Nitrogen

Explanation

To determine which of the following is a noble gas, we need to understand what a noble gas is and identify the options provided.

### Step-by-Step Solution:

1. **Understand the Definition of Noble Gases**:
- Noble gases are elements found in Group 18 of the periodic table.
- They are known for being chemically inert, meaning they do not readily react with other elements.

2. **Characteristics of Noble Gases**:
- Noble gases have completely filled electron shells, which makes them stable.
- Because their outer electron shells are full, they do not have the tendency to gain or lose electrons.

3. **Identify the Options**:
- We need to examine the four options given to see which one belongs to Group 18.

4. **Evaluate Each Option**:
- **Option 1: Hydrogen** - This is in Group 1, so it is not a noble gas.
- **Option 2: Helium** - This is in Group 18 and is a noble gas. Its electron configuration is 1s², indicating a filled shell.
- **Option 3: Oxygen** - This is in Group 16 and does not have a filled outer shell, so it is not a noble gas.
- **Option 4: Nitrogen** - This is in Group 15 and also does not have a filled outer shell, so it is not a noble gas.

5. **Conclusion**:
- The only noble gas among the options provided is **Helium** (Option 2).

### Final Answer:
**Helium is the noble gas.**

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