The correct order of increasing electron affinity of halogens is

Options

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

Explanation

To determine the correct order of increasing electron affinity of halogens, we can follow these steps:

### Step 1: Understand Electron Affinity
Electron affinity is defined as the energy released when one mole of gaseous atoms acquires an electron to form an anion. It reflects how strongly an atom can attract an incoming electron.

### Step 2: Analyze the Halogens
The halogens are located in Group 17 of the periodic table and include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

### Step 3: Consider Atomic Size and Effective Nuclear Charge
As we move down the group from fluorine to iodine:
- The atomic size increases.
- The effective nuclear charge (the net positive charge experienced by electrons) decreases due to increased distance from the nucleus and increased electron shielding.

### Step 4: Relate Atomic Size and Electron Affinity
With an increase in atomic size and a decrease in effective nuclear charge:
- The attraction between the nucleus and the incoming electron weakens.
- Therefore, the electron affinity decreases as we move down the group.

### Step 5: Establish the Order of Electron Affinity
From the above analysis, we can conclude:
- Fluorine has the highest electron affinity because it is the smallest and has the highest effective nuclear charge.
- Chlorine has a lower electron affinity than fluorine but higher than bromine and iodine.
- Bromine has a lower electron affinity than chlorine but higher than iodine.
- Iodine has the lowest electron affinity among the halogens.

Thus, the order of increasing electron affinity for the halogens is:
**Iodine (I) < Bromine (Br) < Chlorine (Cl) < Fluorine (F)**

### Conclusion
The correct order of increasing electron affinity of halogens is:
**I < Br < Cl < F**