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 the lines and the dots in a Lewis diagram stand for, and why core electrons are not drawn. (Guide: “What a Lewis diagram shows”)
- I can explain why hydrogen and fluorine are always outer atoms. (Guide: “A step-by-step method”)
- I can state which atoms can end with fewer than 8 electrons and which can end with more, and why period 2 atoms cannot exceed 8. (Guide: “When the central atom does not end with eight”; Practice Q2, Q7)
- I can explain why one molecular formula can have more than one valid skeleton. (Guide: “One formula, more than one skeleton”)
Skills
- I can count the total valence electrons in a molecule or polyatomic ion, adding or subtracting electrons for the charge. (Practice Q1, Q5)
- I can choose the central atom using electronegativity. (Guide: Worked example 1)
- I can draw a Lewis diagram that needs a double or triple bond. (Guide: Worked examples 1 and 2; Practice Q4)
- I can draw a Lewis diagram for a polyatomic ion with brackets and its charge. (Guide: Worked example 2; Practice Q5)
- I can place leftover electrons on a period 3 or larger central atom to give an expanded octet. (Guide: Worked example 3; Practice Q3, Q7)
- I can use “needed minus available” to predict the number of bonds in an octet molecule. (Guide: “A quick check for multiple bonds”; Practice Q4)
Reasoning
- I can find the error in someone else’s Lewis diagram by recounting the total and each atom’s electrons. (Practice Q6)
- I can justify why a proposed Lewis diagram is impossible, using the period of the central atom. (Practice Q7)
All ticked? Move on to Topic 2.6, Resonance and Formal Charge, or return to the course roadmap.