Which of the following sequence of elements is arranged in the order of increasing atomic radii?

Options

A. `Na, Mg, AI, Si`
B. `C, N, O, F`
C. `O, S, Se, Te`
D. `I, Br, CI, F`

Answer

To determine the correct sequence of elements arranged in the order of increasing atomic radii, we need to analyze the atomic sizes of the elements provided in each option.

### Step-by-Step Solution:

1. **Understanding Atomic Radius**: Atomic radius generally decreases across a period from left to right due to the increase in nuclear charge, which pulls the electrons closer to the nucleus. Conversely, atomic radius increases down a group due to the addition of electron shells.

2. **Analyzing Option A**: The elements are Sodium (Na), Magnesium (Mg), Aluminum (Al), and Silicon (Si).
- These elements are in the third period.
- As we move from Na to Si (left to right), the atomic radius decreases.
- Order: Na > Mg > Al > Si (decreasing order).

3. **Analyzing Option B**: The elements are Carbon (C), Nitrogen (N), Oxygen (O), and Fluorine (F).
- These elements are in the second period.
- As we move from C to F (left to right), the atomic radius decreases.
- Order: C > N > O > F (decreasing order).

4. **Analyzing Option C**: The elements are Oxygen (O), Sulfur (S), Selenium (Se), and Tellurium (Te).
- These elements belong to the same group (16th group).
- As we move down the group from O to Te, the atomic radius increases.
- Order: O < S < Se < Te (increasing order).

5. **Analyzing Option D**: The elements are Iodine (I), Bromine (Br), Chlorine (Cl), and Fluorine (F).
- These elements belong to the same group (17th group).
- As we move down the group from F to I, the atomic radius increases.
- Order: F < Cl < Br < I (increasing order).

6. **Conclusion**:
- From the analysis, Option C (O < S < Se < Te) shows an increasing order of atomic radii.
- Therefore, the correct answer is **Option C**.