Question

The correct decreasing order of negative electron gain enthalpy for C, Ca, Al, F and O is

• A. F $>$ O $>$ C $>$ Al $>$ Ca
• B. Ca $>$ Al $>$ O $>$ F $>$ C
• C. Al $>$ F $>$ Ca $>$ C $>$ O
• D. F $>$ C $>$ O $>$ Ca $>$ Al

Hint:

Halogens and electronegative elements have the most negative electron gain enthalpy. The trend generally decreases as you move down a group and across a period.

Answer 1

The Correct Option is A

Electron gain enthalpy refers to the energy released when an electron is added to a neutral atom in the gas phase. The more negative the electron gain enthalpy, the more likely the atom is to accept an electron. Let's analyze the trend for the elements: 

- Fluorine (F) has the most negative electron gain enthalpy because it is a halogen and easily accepts electrons to complete its octet. 
- Oxygen (O) also has a highly negative electron gain enthalpy, being an electronegative element but slightly less than fluorine due to its larger size.
- Carbon (C) has a moderate electron gain enthalpy, as it is less electronegative than oxygen and fluorine. 
- Aluminium (Al) has a less negative electron gain enthalpy than carbon due to its larger atomic radius and lower electronegativity. 
- Calcium (Ca) has the least negative electron gain enthalpy, as it is an alkaline earth metal and less likely to gain electrons. 

Thus, the correct order is F $>$ O $>$ C $>$ Al $>$ Ca.