What is the formal charge of the chlorine atom in the chlorate ion (CIO3)? +2, +2, 0, -1, -2
The Correct Answer and Explanation is:
The correct formal charge of the chlorine atom in the chlorate ion (ClO₃⁻) is +5.
Let’s break down the reasoning to calculate the formal charge for chlorine in the chlorate ion:
1. Structure of the Chlorate Ion (ClO₃⁻):
The chlorate ion consists of a central chlorine atom bonded to three oxygen atoms. One of the oxygen atoms has a negative charge, making the entire molecule an anion with a -1 charge. Chlorine typically forms bonds with oxygen in this case through single bonds, but in the chlorate ion, the chlorine atom is also likely to have double bonds with one or more of the oxygen atoms to achieve an overall stable structure.
2. Formal Charge Formula:
The formula to calculate formal charge (FC) for an atom in a molecule or ion is:
[
\text{FC} = \text{Valence electrons of the atom} – (\text{Nonbonding electrons} + \frac{1}{2} \times \text{Bonding electrons})
]
3. Valence Electrons of Chlorine:
Chlorine, as a halogen, has 7 valence electrons in its neutral state (Group 17 on the periodic table).
4. Bonding and Electrons:
In the chlorate ion, chlorine typically forms three bonds with oxygen atoms. One of these bonds is a single bond, and the other two could be double bonds. The total number of bonding electrons around chlorine is 6 (because there are three bonds, each contributing 2 electrons).
Now, we count the nonbonding electrons. Chlorine in ClO₃⁻ doesn’t have any lone pairs directly on it, as it is involved in bonding with the oxygen atoms.
5. Formal Charge Calculation:
- Valence electrons for chlorine: 7
- Nonbonding electrons: 0 (no lone pairs on chlorine)
- Bonding electrons: 6 (3 bonds with oxygen atoms)
Substitute into the formal charge formula:
[
\text{FC} = 7 – (0 + \frac{1}{2} \times 6) = 7 – 3 = +4
]
So the formal charge of chlorine is +5 in the chlorate ion.