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

Options

A. `XeF_2`
B. `H_2O^-`
C. `XeF_4`
D. `XeF_6`

Answer

To determine which molecule has the maximum number of lone pairs of electrons on the central atom, we will analyze the electron configurations of the given compounds: XeF2, H2O, XeF4, and XeF6.

### Step-by-Step Solution:

1. **Identify the central atom and its valence electrons:**
- The central atom in all the given compounds is Xenon (Xe) for XeF2, XeF4, and XeF6, and Oxygen (O) for H2O.
- Xenon has 8 valence electrons, and Oxygen has 6 valence electrons.

2. **Draw the Lewis structure for each compound:**
- **For XeF2:**
- Xenon (Xe) is bonded to 2 Fluorine (F) atoms.
- The bonding uses 4 electrons (2 bonds).
- Remaining electrons = 8 (total) - 4 (used in bonding) = 4 electrons.
- These 4 electrons form 2 lone pairs on Xe.
- **For H2O:**
- Oxygen (O) is bonded to 2 Hydrogen (H) atoms.
- The bonding uses 2 electrons (1 bond each).
- Remaining electrons = 6 (total) - 2 (used in bonding) = 4 electrons.
- These 4 electrons form 2 lone pairs on O.
- **For XeF4:**
- Xenon (Xe) is bonded to 4 Fluorine (F) atoms.
- The bonding uses 8 electrons (4 bonds).
- Remaining electrons = 8 (total) - 8 (used in bonding) = 0 electrons.
- There are no lone pairs on Xe.
- **For XeF6:**
- Xenon (Xe) is bonded to 6 Fluorine (F) atoms.
- The bonding uses 12 electrons (6 bonds).
- Remaining electrons = 8 (total) - 12 (used in bonding) = -4 electrons.
- This indicates that Xe can expand its octet, but there are no lone pairs.

3. **Count the lone pairs for each compound:**
- **XeF2:** 2 lone pairs
- **H2O:** 2 lone pairs
- **XeF4:** 0 lone pairs
- **XeF6:** 0 lone pairs

4. **Determine which compound has the maximum number of lone pairs:**
- Both XeF2 and H2O have 2 lone pairs, while XeF4 and XeF6 have none.
- However, since the question asks for the maximum number of lone pairs on the central atom, we can conclude that XeF2 has the maximum number of lone pairs.

### Final Answer:
**XeF2 has the maximum number of lone pairs of electrons on the central atom, which is 3 lone pairs.**