Question

The order of increasing sizes of atomic radii among the elements $O, S, Se$ and $As$ is :

• A. $As < S < O < Se$
• B. $Se < S < As < O$
• C. $O < S < As < Se$
• D. $O < S < Se < As$

Answer 1

The Correct Option is D

To determine the order of increasing sizes of atomic radii among the elements Oxygen (O), Sulfur (S), Selenium (Se), and Arsenic (As), we need to understand the periodic trends in atomic radii:

1. Periodic Trend along a Group: As we move down a group in the periodic table, the atomic radii increase. This is because each subsequent element in a group has an additional electron shell, making the atom larger.
2. Order of Elements: Oxygen (O), Sulfur (S), and Selenium (Se) belong to Group 16 of the periodic table, also known as the chalcogens. Arsenic (As) belongs to Group 15.
3. Comparison within Group 16:
   • In Group 16: O, S, and Se, the atomic radii increase as we move from Oxygen (at the top of the group) to Selenium (further down the group). Thus, the order is O < S < Se.
4. Comparison between Groups:
   • Arsenic (As) is actually further down in the periodic table than Selenium (Se) since it belongs to Group 15. Hence, As will have a larger atomic radius than Se.

Combining these observations, we establish that the order of increasing atomic radii is: O < S < Se < As.

Therefore, the correct answer is the option: O < S < Se < As.