Which halogen requires least energy for excitation

Options

A. F
B. Cl
C. Br
D. I

Explanation

To determine which halogen requires the least energy for excitation, we can follow these steps:

### Step 1: Understand the Concept of Excitation
Excitation refers to the process of promoting an electron to a higher energy level. The energy required for this process depends on the distance of the electron from the nucleus and the effective nuclear charge experienced by the electron.

**Hint:** Remember that the energy required for excitation is influenced by the atomic size and the number of electron shells.

### Step 2: Analyze the Halogens
The halogens include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). As we move down the group in the periodic table, the atomic size increases due to the addition of electron shells.

**Hint:** Consider how the atomic size changes as you move down the group of halogens.

### Step 3: Compare Atomic Sizes
- **Fluorine (F)**: Smallest atomic radius
- **Chlorine (Cl)**: Larger than F
- **Bromine (Br)**: Larger than Cl
- **Iodine (I)**: Largest atomic radius

As the atomic radius increases, the distance of the valence electrons from the nucleus also increases.

**Hint:** Larger atomic size generally means that the valence electrons are held less tightly by the nucleus.

### Step 4: Determine the Energy Requirement
Since iodine has the largest atomic radius among the halogens, its valence electrons are farther from the nucleus. This means that they experience a weaker attraction from the nucleus, requiring less energy to be excited to a higher energy level.

**Hint:** The halogen with the largest atomic radius will typically require the least energy for excitation.

### Step 5: Conclusion
Based on the analysis, iodine (I) requires the least energy for excitation because it has the largest atomic size and the least effective nuclear charge acting on its valence electrons.

**Final Answer:** Iodine (I) requires the least energy for excitation.