Question:medium
Which one of the following is the correct decreasing order for the magnitude of Electron Gain Enthalpy \((\Delta_{eg}H)\) for the elements given below?
Which one of the following is the correct decreasing order for the magnitude of Electron Gain Enthalpy \((\Delta_{eg}H)\) for the elements given below?
Show Hint
Among halogens, chlorine has the highest magnitude of electron gain enthalpy because fluorine's very small size causes strong electron-electron repulsion in its compact \(2p\) orbital.
Updated On: Jun 5, 2026
- \( Br > Cl > At > I \)
- \( Cl > Br > I > At \)
- \( I > Br > Cl > At \)
- \( At > Br > Cl > I \)
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Set up the idea.
Electron gain enthalpy tells how much energy is let out when an atom grabs an extra electron. A bigger size of this value means the atom pulls the electron in more eagerly. All four atoms here are halogens.
Step 2: General group trend.
Going down group 17 the atoms get larger and the outer shell sits farther from the nucleus, so the pull on a new electron weakens. That means the value should drop from Cl down to At.
Step 3: The small twist at chlorine.
Chlorine usually tops the list rather than fluorine because chlorine's larger shell has less electron crowding. Among the four given, chlorine is the strongest grabber.
Step 4: Order the rest by size.
After Cl comes Br, then I, then At, each one larger and weaker than the last.
Step 5: Answer.
So the decreasing order is \[ \boxed{Cl > Br > I > At} \]
Electron gain enthalpy tells how much energy is let out when an atom grabs an extra electron. A bigger size of this value means the atom pulls the electron in more eagerly. All four atoms here are halogens.
Step 2: General group trend.
Going down group 17 the atoms get larger and the outer shell sits farther from the nucleus, so the pull on a new electron weakens. That means the value should drop from Cl down to At.
Step 3: The small twist at chlorine.
Chlorine usually tops the list rather than fluorine because chlorine's larger shell has less electron crowding. Among the four given, chlorine is the strongest grabber.
Step 4: Order the rest by size.
After Cl comes Br, then I, then At, each one larger and weaker than the last.
Step 5: Answer.
So the decreasing order is \[ \boxed{Cl > Br > I > At} \]
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