Draw the Lewis structure for the chlorate ion (ClO3-). b) What is the average formal charge on each oxygen atom? c) Provide the AXnEm classification and descriptive geometry name of ClO3-.
The Correct Answer and Explanation is:
To draw the Lewis structure for the chlorate ion, follow these steps:
- Count the total valence electrons:
- Cl = 7 valence electrons
- O = 6 valence electrons × 3 = 18
- Add 1 extra electron due to the negative charge
→ Total = 7 + 18 + 1 = 26 valence electrons
- Choose the central atom:
Chlorine (Cl) is less electronegative than oxygen, so it is the central atom. - Create single bonds between Cl and each O:
Each single bond uses 2 electrons × 3 bonds = 6 electrons
→ 26 − 6 = 20 electrons remain - Distribute remaining electrons to satisfy octets:
Place 6 electrons (3 lone pairs) on each O → 6 × 3 = 18 electrons
→ 20 − 18 = 2 electrons remain - Place the last 2 electrons on chlorine as a lone pair.
- Check the octets:
Oxygen atoms are satisfied with 8 electrons.
Chlorine has 3 bonds + 1 lone pair = 8 electrons. But chlorine can expand its octet (period 3 element), so form one double bond with one O to minimize formal charges.
Final structure: Cl with one double bond and two single bonds to three oxygen atoms. The structure includes one negative formal charge on each singly bonded oxygen.
b) Average Formal Charge on Each Oxygen Atom:
- One oxygen has a double bond, formal charge = 0
- Two oxygens have single bonds, each with a formal charge of -1
Average formal charge on oxygen:0+(−1)+(−1)3=−23=−23\frac{0 + (-1) + (-1)}{3} = \frac{-2}{3} = \boxed{-\dfrac{2}{3}}30+(−1)+(−1)=3−2=−32
c) AXₙEₘ Classification and Geometry:
- Central atom (Cl) is bonded to 3 atoms (O) → X₃
- Has 1 lone pair → E₁
→ AX₃E₁
Descriptive Geometry Name:
AX₃E₁ corresponds to a trigonal pyramidal molecular geometry.
Summary:
- Lewis Structure: One double bond and two single bonds around Cl, total 26 valence electrons.
- Average Formal Charge on O: −23-\dfrac{2}{3}−32
- Molecular Shape: AX₃E₁, Trigonal Pyramidal.
