The order of electron gain enthalpy of VI A group elements is

Options

A. `S gt Se gt Te gt Po gt O`
B. `S gt Se gt Te gt O gt Po`
C. `O gt Se gt S gt Te gt Po`
D. `O gt Te gt Se gt S gt Po`

Answer

To determine the order of electron gain enthalpy of the VI A group elements (also known as the chalcogens or oxygen family), we need to analyze the trends in electron gain enthalpy across this group.

### Step-by-Step Solution:

1. **Understanding Electron Gain Enthalpy**:
- Electron gain enthalpy is defined as the amount of energy released when an atom in the gaseous state accepts an electron to form a negative ion. A more negative value indicates a greater tendency to gain an electron.

2. **Group VI A Elements**:
- The elements in Group VI A are Oxygen (O), Sulfur (S), Selenium (Se), Tellurium (Te), and Polonium (Po).

3. **Trend in Electron Gain Enthalpy**:
- As we move down the group from Oxygen to Polonium, the size of the atoms increases. This increase in atomic size leads to a decrease in the effective nuclear charge experienced by the incoming electron due to increased electron shielding.

4. **Oxygen's Anomaly**:
- Oxygen has a smaller atomic size compared to the other elements in the group, which leads to higher electron-electron repulsion when an additional electron is added. This results in a lower (less negative) electron gain enthalpy for Oxygen compared to what might be expected.

5. **Order of Electron Gain Enthalpy**:
- Based on the above points, the order of electron gain enthalpy from most negative to least negative is as follows:
- Sulfur (S) > Selenium (Se) > Tellurium (Te) > Polonium (Po) > Oxygen (O)
- Therefore, the increasing order of electron gain enthalpy is:
- O < Po < Te < Se < S

### Final Answer:
The order of electron gain enthalpy of VI A group elements is:
**O < Po < Te < Se < S**