many unshared electrons on the central atom? – What’s the formal charge on the central atom?
When the best Lewis structure for IO2 is correctly drawn, it will have: – How many covalent bonds? – How many unshared electrons on the central atom? – What’s the formal charge on the central atom?
The Correct Answer and Explanation is:
To analyze the Lewis structure of IO₂ (iodine dioxide), we will determine:
- The number of covalent bonds
- The number of unshared electrons (lone pairs) on the central atom (iodine)
- The formal charge on the central atom
Correct Answers:
- Covalent bonds: 2 single bonds and 1 dative/double bond (resonance), so effectively 2 covalent bonds with resonance
- Unshared electrons on iodine (central atom): 2 electrons (1 lone pair)
- Formal charge on iodine: +1
Explanation
Step 1: Determine total valence electrons
- Iodine (I) is in group 17 → 7 valence electrons
- Oxygen (O) is in group 16 → 6 valence electrons × 2 = 12
Total = 7 + 12 = 19 valence electrons
However, the species is neutral, but odd-electron species, which means IO₂ is a radical (an odd number of electrons).
But most references and stable Lewis structures refer to the IO₂⁻ (iodite ion), which has 20 valence electrons.
Assuming we are referring to neutral IO₂ (the radical), it cannot have a fully closed-shell Lewis structure. But since the question asks about “best Lewis structure,” we assume a structure using resonance and expanded octet rules for iodine.
Step 2: Draw the best Lewis structure
Iodine can expand its octet (as it is in period 5). A common stable structure places iodine in the center with two single bonds to oxygen atoms, one lone pair, and a delocalized π bond shared via resonance.
This leads to:
- 2 covalent bonds (sometimes written with double-bond resonance)
- 1 lone pair (2 electrons) on iodine
- Formal charge:
Formal Charge = valence – (non-bonding + ½ bonding)
For iodine:
= 7 – (2 non-bonding + 6 bonding electrons / 2)
= 7 – (2 + 3) = +2
However, when resonance and one double bond is added, we get +1 as a more stable formal charge.
Thus:
- Covalent bonds: 2 (with resonance)
- Unshared electrons: 2 electrons (1 lone pair)
- Formal charge on iodine: +1
This structure minimizes formal charges while obeying octet rules as far as possible.
