Question

Electron gain enthalpy provides a measure of the

ease with which an atom adds an electron to form

anion. From the following select the element to

which addition of an extra electron to gaseous

atom leads to absorption of energy.

(1) Na (2) Al

(3) Xe (4) F​

Answer 1

Answer:

The electron gain enthalpy of an element is a measure of the firmness or strength with which an extraelectron is bound to it. It is measured in electron volts per atom or kJ per mole.

Answer 2

The correct answer is Xenon (OPTION C).

• Electron gain enthalpy is the minimum amount of energy that is released when an electron is added into an atom to form an anion.

• Electron gain enthalpy is generally negative.  

• A Negative sign of electron gain enthalpy implies energy is being released.

• The value of the negative sign is more for the electrons which are near to noble configuration/octet configuration.

• Since Xenon belongs to the 18th group, It already has a stable configuration and it doesn't require any addition/removal of am electron.

• The addition of an electron to a stable configuration leads to the absorption of energy.  
• From the given Options, Xenon is the only option with Octet configuration. Therefore, the addition of an electron to Xenon leads to the absorption of energy. A s a new shell has to be added for adding another electron which requires a lot of energy.

Therefore, Option 3 (XENON) is the correct option.