Which of the following molecules is not an exception to octet rule?

Options

A. `BF_(3)`
B. `PF_(5)`
C. `CO_(2)`
D. `IF_(7)`

Answer

To determine which of the given molecules is not an exception to the octet rule, we will analyze each option step by step.

### Step 1: Understand the Octet Rule
The octet rule states that atoms tend to bond in such a way that they have eight electrons in their valence shell, achieving a stable electron configuration similar to that of noble gases.

### Step 2: Analyze Each Option

#### Option A: BF3
1. **Identify the central atom**: Boron (B).
2. **Count valence electrons**: Boron has 3 valence electrons, and each Fluorine (F) has 7 valence electrons.
3. **Draw the Lewis structure**: Boron forms three bonds with three Fluorine atoms.
4. **Count electrons around Boron**: After bonding, Boron has only 6 electrons in its valence shell (3 from B and 3 from F).
5. **Conclusion**: BF3 does not satisfy the octet rule (hypovalent).

#### Option B: PF5
1. **Identify the central atom**: Phosphorus (P).
2. **Count valence electrons**: Phosphorus has 5 valence electrons, and each Fluorine has 7.
3. **Draw the Lewis structure**: Phosphorus forms five bonds with five Fluorine atoms.
4. **Count electrons around Phosphorus**: After bonding, Phosphorus has 10 electrons in its valence shell (5 from P and 5 from F).
5. **Conclusion**: PF5 does not satisfy the octet rule (hypervalent).

#### Option C: CO2
1. **Identify the central atom**: Carbon (C).
2. **Count valence electrons**: Carbon has 4 valence electrons, and each Oxygen (O) has 6.
3. **Draw the Lewis structure**: Carbon forms double bonds with two Oxygen atoms.
4. **Count electrons around Carbon**: After bonding, Carbon has 8 electrons in its valence shell (4 from C and 4 from O).
5. **Conclusion**: CO2 satisfies the octet rule.

#### Option D: IF7
1. **Identify the central atom**: Iodine (I).
2. **Count valence electrons**: Iodine has 7 valence electrons, and each Fluorine has 7.
3. **Draw the Lewis structure**: Iodine forms seven bonds with seven Fluorine atoms.
4. **Count electrons around Iodine**: After bonding, Iodine has 14 electrons in its valence shell (7 from I and 7 from F).
5. **Conclusion**: IF7 does not satisfy the octet rule (hypervalent).

### Final Conclusion
Among the options analyzed, only **CO2** satisfies the octet rule. Therefore, the answer to the question is **Option C: CO2**.

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