Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions.
Understanding
- I can explain what a resonance hybrid is, and why the molecule does not switch between its resonance structures. (Guide: “The resonance hybrid”)
- I can explain why resonance is needed to predict bond lengths, bond energies and where the charge is. (Guide: Worked example 1; Practice Q5)
- I can explain what formal charge assumes, and why it is not the real charge on an atom. (Guide: “Formal charge”)
- I can explain why species with an odd number of valence electrons show a limitation of the Lewis model. (Guide: Worked example 3; Practice Q7)
Skills
- I can draw all the equivalent resonance structures of a molecule or ion. (Guide: Worked example 1; Practice Q4, Q5)
- I can calculate the average bond order from resonance structures, including cases such as nitrate where it is not 1.5. (Practice Q2)
- I can calculate the formal charge on every atom and check that the sum equals the overall charge. (Practice Q1, Q6)
- I can rank bond lengths using bond orders from Lewis diagrams. (Practice Q3, Q5)
Reasoning
- I can use formal charge to choose between two possible skeletons. (Guide: Worked example 2; Practice Q6)
- I can rank nonequivalent resonance structures using the octet rule, the size of the formal charges and electronegativity. (Guide: Worked example 2; Practice Q4)
- I can explain what to do when the octet rule and formal charge favour different diagrams. (Guide: “When the octet rule and formal charge disagree”)
- I can evaluate a claim about a molecule’s structure using resonance or formal charge as evidence. (Practice Q5, Q7)
All ticked? Move on to Topic 2.7, VSEPR and Hybridization, or return to the course roadmap.