Which of the following has zero valency?

Options

A. Be
B. Se
C. Li
D. Ar

Explanation

To determine which of the given elements has zero valency, we need to analyze the electronic configurations and valency of each element listed. The elements provided are beryllium, selenium, lithium, and argon.

### Step-by-Step Solution:

1. **Identify the Elements and Their Atomic Numbers:**
- Beryllium (Be) - Atomic number 4
- Selenium (Se) - Atomic number 34
- Lithium (Li) - Atomic number 3
- Argon (Ar) - Atomic number 18

2. **Determine the Electronic Configurations:**
- **Beryllium (Be)**:
- Atomic number 4 → Electronic configuration: 1s² 2s²
- **Selenium (Se)**:
- Atomic number 34 → Electronic configuration: [Ar] 3d¹⁰ 4s² 4p⁴
- **Lithium (Li)**:
- Atomic number 3 → Electronic configuration: 1s² 2s¹
- **Argon (Ar)**:
- Atomic number 18 → Electronic configuration: 1s² 2s² 2p⁶ 3s² 3p⁶

3. **Analyze the Valency of Each Element:**
- **Beryllium (Be)**:
- Has 4 electrons in its outer shell (2s²). It can lose 2 electrons to achieve a stable configuration, so its valency is +2.
- **Selenium (Se)**:
- As a group 16 element, it has 6 electrons in its outer shell (4s² 4p⁴) and can gain 2 electrons to complete its octet. Thus, its valency is -2.
- **Lithium (Li)**:
- Has 1 electron in its outer shell (2s¹). It can lose this electron to achieve a stable configuration, so its valency is +1.
- **Argon (Ar)**:
- Has a complete outer shell with 8 electrons (3s² 3p⁶). Since it does not need to gain or lose any electrons, its valency is 0.

4. **Conclusion:**
- Among the elements analyzed, **argon (Ar)** is the only element that has zero valency, as it is a noble gas with a complete octet.

### Final Answer:
**D) Argon (Ar)** has zero valency.