Which of the following is the correct order of size of the given species?

Options

A. `IgtI^-gtI^+`
B. `I^+gtI^-gtI`
C. `IgtI^+gtI^-`
D. `I^-gtI^+gtI`

Answer

To determine the correct order of size for the given species (Iodine anion, neutral iodine, and iodine cation), we need to analyze how the size of an atom changes when it gains or loses electrons.

### Step-by-Step Solution:

1. **Identify the Species**: We have three species of iodine:
- Iodine anion (I⁻)
- Neutral iodine (I)
- Iodine cation (I⁺)

2. **Understand Electron Gain and Loss**:
- An anion (I⁻) is formed when an atom gains an electron.
- A cation (I⁺) is formed when an atom loses an electron.

3. **Effect of Gaining Electrons (Anion)**:
- When iodine gains an electron to become I⁻, the number of electrons increases while the number of protons remains the same.
- This leads to a decrease in the effective nuclear charge experienced by the outermost electrons because the increased electron-electron repulsion outweighs the attraction from the nucleus.
- As a result, the size of the anion (I⁻) increases.

4. **Effect of Losing Electrons (Cation)**:
- When iodine loses an electron to become I⁺, the number of electrons decreases while the number of protons remains the same.
- This results in an increase in the effective nuclear charge experienced by the remaining electrons, leading to a stronger attraction between the nucleus and the electrons.
- Consequently, the size of the cation (I⁺) decreases.

5. **Size Comparison**:
- Based on the above points, we can summarize the sizes as follows:
- I⁻ (anion) > I (neutral) > I⁺ (cation)
- Therefore, the order of size from largest to smallest is: I⁻ > I > I⁺.

### Final Answer:
The correct order of size of the given species is: **I⁻ > I > I⁺**.