`P` is a noble gas which has two electrons in its valence shell, `Q` is the lightest noble gas having eight electrons in its valence shell and `S` is the most abundant noble gas in the atmosphere. `P, Q` and `R` are respectively

Options

A. Hydrogen, helium and argon
B. Helium, neon and argon
C. Helium, argon and neon
D. Neon, argon and krypton.

Answer

To solve the question, we need to identify the noble gases `P`, `Q`, and `R` based on the given descriptions.

### Step-by-Step Solution:

1. **Identify `P`:**
- `P` is a noble gas with two electrons in its valence shell.
- The only noble gas with two electrons in its valence shell is **Helium (He)**.
- Therefore, `P = Helium`.

2. **Identify `Q`:**
- `Q` is described as the lightest noble gas having eight electrons in its valence shell.
- The lightest noble gas with eight electrons in its valence shell is **Neon (Ne)**.
- Therefore, `Q = Neon`.

3. **Identify `R`:**
- `R` is the most abundant noble gas in the atmosphere.
- The most abundant noble gas in the atmosphere is **Argon (Ar)**.
- Therefore, `R = Argon`.

### Final Answer:
- `P = Helium (He)`
- `Q = Neon (Ne)`
- `R = Argon (Ar)`