The correct order of atomic sizes is

Options

A. `Be gt C gt F gt Ne`
B. `Be lt C lt F lt Ne`
C. `Be gt C gt F lt Ne`
D. `F lt Ne lt Be lt C`

Answer

To determine the correct order of atomic sizes for the elements Beryllium (Be), Carbon (C), Fluorine (F), and Neon (Ne), we need to consider the periodic trends in atomic size.

### Step-by-Step Solution:

1. **Understanding Atomic Size**: Atomic size generally refers to the distance from the nucleus to the outermost shell of electrons. As we move across a period in the periodic table from left to right, atomic size tends to decrease.

2. **Identify the Elements and Their Positions**:
- Beryllium (Be) is in Group 2 (alkaline earth metals).
- Carbon (C) is in Group 14.
- Fluorine (F) is in Group 17 (halogens).
- Neon (Ne) is in Group 18 (noble gases).

3. **Trends Across a Period**: As we move from Beryllium to Neon across the second period:
- The effective nuclear charge increases because the number of protons in the nucleus increases while the shielding effect remains relatively constant.
- This increased nuclear charge pulls the electrons closer to the nucleus, resulting in a decrease in atomic size.

4. **Comparing Atomic Sizes**:
- Beryllium (Be) has the largest atomic size among the four because it is the furthest left in the period.
- Carbon (C) is smaller than Beryllium.
- Fluorine (F) is smaller than Carbon.
- Neon (Ne), being a noble gas, has the smallest atomic size in this group.

5. **Final Order of Atomic Sizes**: Based on the above reasoning, the order of atomic sizes from largest to smallest is:
- Be > C > F > Ne

### Conclusion:
The correct order of atomic sizes is: **Beryllium (Be) > Carbon (C) > Fluorine (F) > Neon (Ne)**.