What is the formal charge on each atom in CBr2F2? a. C = 0, Br = 0, F = 0 b. C = 0, Br = -1, F = +1 c. C = 0, Br = +1, F = -1 d. C = -2, Br = +1, F = +1 e. C = +4, Br = -1, F = -1
The Correct Answer and Explanation is:
The correct answer is a. C = 0, Br = 0, F = 0.
Explanation:
Formal charge is a concept used in chemistry to determine the distribution of electrons within a molecule. It helps assess whether atoms bear extra electrons or have lost electrons in a covalent bonding arrangement. The formal charge (FCFC) on an atom is calculated using the formula:
FC=Valence electrons−Nonbonding electrons−Bonding electrons2FC = \text{Valence electrons} – \text{Nonbonding electrons} – \frac{\text{Bonding electrons}}{2}
For carbon (C) in CBr₂F₂:
- Carbon has 4 valence electrons.
- It forms four single bonds (two with bromine and two with fluorine).
- Carbon does not have nonbonding electrons.
- Bonding electrons = 8 (four single bonds, each containing two electrons).
FC=4−0−82=0FC = 4 – 0 – \frac{8}{2} = 0
For bromine (Br):
- Bromine belongs to Group 17 and has 7 valence electrons.
- In this molecule, each bromine atom forms a single bond with carbon.
- Bromine has six nonbonding electrons (three lone pairs).
- Bonding electrons = 2 (one single bond).
FC=7−6−22=0FC = 7 – 6 – \frac{2}{2} = 0
For fluorine (F):
- Fluorine also belongs to Group 17 and has 7 valence electrons.
- It forms a single bond with carbon.
- Fluorine retains six nonbonding electrons.
- Bonding electrons = 2 (one single bond).
FC=7−6−22=0FC = 7 – 6 – \frac{2}{2} = 0
Since all atoms have a formal charge of zero, CBr₂F₂ is a neutral molecule with a stable electron distribution. The formal charge analysis confirms that option (a) is correct.
