While going down in the group of non-metals (14, 15, 16 and 17) the electronegative character of non-metals decreases. Typical example is of group 15 elements. The elements nitrogen (2nd period) and phosphorus (3rd period) are non-metals and their oxides are acidic in nature. The elements arsenic (4th period) and antimony (5th period) are metalloids and their oxides are amphoteric in nature. However, bismuth (6th period) is a metal. Thus, we can see that the electronegative character (non-metallic character) of elements gradually decreases and ultimately the last element becomes metal. In case of group 17 of halogens, the first member of the group i.e., fluorine is most non-metallic in character and last member of group, i.e., astatine is least non-metallic in character. In other words, the electronegative nature of the elements decreases as we move down the group.
Which of the following is the most non-metallic element?

Options

A. F
B. Cl
C. Br
D. I

Answer

To determine which of the following is the most non-metallic element, we need to understand the concept of non-metallic character and how it varies within groups in the periodic table.

### Step-by-Step Solution:

1. **Understanding Non-Metallic Character**:
- Non-metallic character refers to the tendency of an element to gain electrons. Non-metals are typically found on the right side of the periodic table.

2. **Identifying the Group**:
- The question refers to elements from Group 17 (the halogens), which includes fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

3. **Trends in Non-Metallic Character**:
- As we move down a group in the periodic table, the atomic size increases. This increase in size leads to a decrease in the effective nuclear charge (Z effective) experienced by the outermost electrons.
- A smaller atomic size means that the nucleus can exert a stronger pull on the valence electrons, making it easier for the element to gain electrons and thus exhibit a higher non-metallic character.

4. **Comparing the Elements**:
- Among the halogens:
- **Fluorine (F)** is the smallest and has the highest non-metallic character.
- **Chlorine (Cl)** is larger than fluorine but still non-metallic.
- **Bromine (Br)** and **Iodine (I)** continue to increase in size and decrease in non-metallic character.
- **Astatine (At)** is the largest and has the least non-metallic character among the halogens.

5. **Conclusion**:
- Therefore, the most non-metallic element among the options given (assuming they are halogens) is **Fluorine (F)**.

### Final Answer:
**Fluorine (F)** is the most non-metallic element.