The order of increasing size of atomic radii among the elements O,S,Se and As

Options

A. `AsltSltOltSe`
B. `SeltSltAsltO`
C. `OltSltAsltSe`
D. `OltSltSeltAs`

Answer

To determine the order of increasing atomic radii among the elements O (Oxygen), S (Sulfur), Se (Selenium), and As (Arsenic), we can follow these steps:

### Step 1: Understand the Periodic Trends
Atomic radius generally increases down a group and decreases across a period in the periodic table. This is due to the increasing number of electron shells as you move down a group and the increasing nuclear charge as you move across a period.

### Step 2: Identify the Group and Period of Each Element
- Oxygen (O) is in Group 16 and Period 2.
- Sulfur (S) is in Group 16 and Period 3.
- Selenium (Se) is in Group 16 and Period 4.
- Arsenic (As) is in Group 15 and Period 4.

### Step 3: Compare the Atomic Radii
- **Oxygen (O)**: Being in Period 2, it has the smallest atomic radius among these elements.
- **Sulfur (S)**: In Period 3, it has a larger atomic radius than Oxygen.
- **Selenium (Se)**: In Period 4, it has a larger atomic radius than Sulfur.
- **Arsenic (As)**: Although Arsenic is in Group 15, it is also in Period 4, and its atomic radius is generally larger than that of Selenium.

### Step 4: Arrange the Elements in Order of Increasing Atomic Radii
Based on the above comparisons, the order of increasing atomic radii is:
1. Oxygen (O)
2. Sulfur (S)
3. Selenium (Se)
4. Arsenic (As)

### Final Answer
The order of increasing size of atomic radii among the elements O, S, Se, and As is:
**O < S < Se < As**

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