Elements P, Q, R and Shave atomic numbers 11, 15, 17 and 18 respectively. Which of them are reactive non-metals?

Options

A. P and Q
B. P and R
C. Q and R
D. R and S

Explanation

To determine which of the elements P, Q, R, and S are reactive non-metals, we will analyze their atomic numbers and electronic configurations.

### Step 1: Identify the elements and their atomic numbers
- Element P: Atomic number 11
- Element Q: Atomic number 15
- Element R: Atomic number 17
- Element S: Atomic number 18

### Step 2: Determine the electronic configurations
1. **Element P (Atomic number 11)**:
- Electronic configuration: 2, 8, 1
- This configuration indicates that P has one electron in its outermost shell. It is likely to lose this electron to achieve a stable configuration (noble gas configuration of Neon, which is 2, 8).

2. **Element Q (Atomic number 15)**:
- Electronic configuration: 2, 8, 5
- Q has five electrons in its outermost shell. To achieve a stable configuration (noble gas configuration of Argon, which is 2, 8, 8), it needs to gain three electrons.

3. **Element R (Atomic number 17)**:
- Electronic configuration: 2, 8, 7
- R has seven electrons in its outermost shell. It needs to gain one electron to achieve a stable configuration (noble gas configuration of Argon, which is 2, 8, 8).

4. **Element S (Atomic number 18)**:
- Electronic configuration: 2, 8, 8
- S already has a complete outer shell and does not need to gain or lose any electrons, indicating it is stable and non-reactive.

### Step 3: Classify the elements
- **Element P**: Since it has a tendency to lose electrons, it is a metal and not a non-metal.
- **Element Q**: It has a tendency to gain three electrons, indicating that it is a non-metal and reactive.
- **Element R**: It has a tendency to gain one electron, indicating that it is also a non-metal and reactive.
- **Element S**: It is stable and does not react, so it is a non-metal but not reactive.

### Step 4: Conclusion
The reactive non-metals among the elements are **Q and R**.

### Final Answer:
**Q and R are the reactive non-metals.**

---