Which species has the maximum number of lone pair of electrons on the central atom ?

Options

A. `CaCO_(3)`
B. `XeF_(4)`
C. `SF_(4)`
D. `KI_(3)`

Explanation

To determine which species has the maximum number of lone pairs of electrons on the central atom, we will analyze the given species one by one.

### Step 1: Analyze CO2^2-
- **Valence Electrons Calculation**:
- Carbon (C) has 4 valence electrons.
- Each Oxygen (O) has 6 valence electrons, and there are 3 O atoms.
- There are 2 extra electrons due to the 2 negative charges.
- Total = 4 (C) + 3*6 (O) + 2 (extra) = 4 + 18 + 2 = 24 electrons.

- **Bonding**:
- Connect C to 3 O atoms with single bonds (3 bond pairs).
- Remaining electrons = 24 - 6 (3 bond pairs) = 18 electrons (or 9 pairs).

- **Lone Pairs**:
- Carbon can form 4 bonds, and it has used 3, so it can form 1 more bond.
- Thus, C has 0 lone pairs.
- The O atoms will have lone pairs to complete their octets.

### Step 2: Analyze CF4
- **Valence Electrons Calculation**:
- Carbon (C) has 4 valence electrons.
- Each Fluorine (F) has 7 valence electrons, and there are 4 F atoms.
- Total = 4 (C) + 4*7 (F) = 4 + 28 = 32 electrons.

- **Bonding**:
- Connect C to 4 F atoms with single bonds (4 bond pairs).
- Remaining electrons = 32 - 8 (4 bond pairs) = 24 electrons (or 12 pairs).

- **Lone Pairs**:
- C has used all its valence electrons in bonding (4 bonds), so it has 0 lone pairs.
- Each F atom will have 3 lone pairs to complete their octets.

### Step 3: Analyze SF4
- **Valence Electrons Calculation**:
- Sulfur (S) has 6 valence electrons.
- Each Fluorine (F) has 7 valence electrons, and there are 4 F atoms.
- Total = 6 (S) + 4*7 (F) = 6 + 28 = 34 electrons.

- **Bonding**:
- Connect S to 4 F atoms with single bonds (4 bond pairs).
- Remaining electrons = 34 - 8 (4 bond pairs) = 26 electrons (or 13 pairs).

- **Lone Pairs**:
- S has used 4 electrons in bonding, so it has 2 lone pairs remaining.

### Step 4: Analyze I3^-
- **Valence Electrons Calculation**:
- Iodine (I) has 7 valence electrons, and there are 3 I atoms.
- There is an extra negative charge contributing 1 more electron.
- Total = 3*7 (I) + 1 (extra) = 21 + 1 = 22 electrons.

- **Bonding**:
- Central Iodine connects to 2 other Iodines (2 bond pairs).
- Remaining electrons = 22 - 4 (2 bond pairs) = 18 electrons (or 9 pairs).

- **Lone Pairs**:
- The central Iodine has 3 lone pairs remaining after bonding.

### Conclusion
After analyzing all species:
- CO2^2- has 0 lone pairs.
- CF4 has 0 lone pairs.
- SF4 has 1 lone pair.
- I3^- has 3 lone pairs.

Thus, the species with the maximum number of lone pairs on the central atom is **I3^-**.

### Final Answer
**I3^- has the maximum number of lone pairs of electrons on the central atom, which is 3.**

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