The `EA` order for halogen is

Options

A. `F gt Cl gt Br gt I`
B. `F lt Cl lt Br lt I`
C. `F lt Cl gt Br gt I`
D. `F gt Cl lt Br gt I`

Answer

To determine the order of electron affinity (EA) for halogens (fluorine, chlorine, bromine, and iodine), we need to consider the concept of electron gain enthalpy. Here's a step-by-step solution:

### Step 1: Understand Electron Affinity
Electron affinity is defined as the energy released when one mole of electrons is added to one mole of gaseous atoms of an element. A more negative value indicates a greater tendency to gain an electron.

### Step 2: Identify the Halogens
The halogens we are considering are:
- Fluorine (F)
- Chlorine (Cl)
- Bromine (Br)
- Iodine (I)

### Step 3: Analyze the Size of Atoms
As we move down the group from fluorine to iodine, the size of the atoms increases:
- Fluorine is the smallest.
- Chlorine is larger than fluorine.
- Bromine is larger than chlorine.
- Iodine is the largest.

### Step 4: Consider Electron-Electron Repulsion
In smaller atoms like fluorine, when an electron is added, the added electron experiences significant electron-electron repulsion due to being close to the nucleus and other electrons. This repulsion reduces the stability of the added electron.

### Step 5: Compare Electron Affinities
- **Chlorine (Cl)**: Despite being larger than fluorine, chlorine has a more favorable electron affinity because the added electron experiences less repulsion compared to fluorine.
- **Fluorine (F)**: Although it has a high electron affinity, the repulsion in its small size makes its electron affinity less negative than that of chlorine.
- **Bromine (Br)**: As we move to bromine, the electron affinity is less negative than chlorine and fluorine due to increased atomic size and reduced effective nuclear charge felt by the added electron.
- **Iodine (I)**: Iodine has the least negative electron affinity due to its larger size and the corresponding decrease in effective nuclear charge.

### Step 6: Establish the Order
Based on the analysis:
- Chlorine (Cl) has the highest electron affinity.
- Fluorine (F) is next.
- Bromine (Br) follows.
- Iodine (I) has the least negative electron affinity.

### Final Order of Electron Affinity
The order of electron affinity for halogens is:
**Cl > F > Br > I**