1. CH₂Cl₂: Carbon is central, bonded to two H and two Cl atoms. All atoms have complete octets (C with 4 single bonds, H with 1 bond, Cl with 3 lone pairs + 1 bond). No resonance.
2. HClO₄(aq): Central Cl bonded to four O atoms (one with double bond, three with single bonds) and one H bonded to an O. The three single-bonded O atoms each have three lone pairs and a negative formal charge; the double-bonded O has two lone pairs. The H is attached to one of the single-bonded O atoms. Resonance exists: the double bond can be with any of the four O atoms, so there are four equivalent resonance structures.
3. N₂: Two N atoms triple-bonded to each other, each with one lone pair. No resonance.
4. PBr₃: Central P bonded to three Br atoms with single bonds. P has one lone pair. Each Br has three lone pairs. No resonance.
5. PCl₅: Central P bonded to five Cl atoms with single bonds. P has no lone pairs (expanded octet). Each Cl has three lone pairs. No resonance.
6. H₃O⁺: Central O bonded to three H atoms with single bonds. O has one lone pair and a +1 formal charge. No resonance.
7. SO₃²⁻: Central S bonded to three O atoms. One double bond to O (two lone pairs), two single bonds to O (each with three lone pairs and -1 formal charge). S has one lone pair and +1 formal charge. Resonance: the double bond can be with any of the three O atoms, so there are three resonance structures.
8. BF₄⁻: Central B bonded to four F atoms with single bonds. B has no lone pairs (incomplete octet). Each F has three lone pairs. Overall charge -1 on ion. No resonance.
9. XeF₄: Central Xe bonded to four F atoms with single bonds. Xe has two lone pairs (square planar geometry). Each F has three lone pairs. No resonance.
10. POCl₃: Central P bonded to one O (double bond) and three Cl atoms (single bonds). P has no lone pairs. O has two lone pairs. Each Cl has three lone pairs. No resonance.
11. H₃PO₄(aq): Central P bonded to four O atoms (one double bond, three single bonds). The three single-bonded O atoms each have one H atom attached. Double-bonded O has two lone pairs. Single-bonded O atoms each have two lone pairs. No resonance (the structure is fixed due to H attachment).
12. I₃⁻: Central I bonded to two terminal I atoms with single bonds. Central I has three lone pairs and -1 formal charge. Each terminal I has three lone pairs. Resonance: the negative charge can be on either terminal I, so two resonance structures exist.
13. COBr₂: Central C double-bonded to O and single-bonded to two Br atoms. C has no lone pairs. O has two lone pairs. Each Br has three lone pairs. No resonance.
Parent Tip: Review the logic above to help your child master the concept of lewis structures worksheet.
