Lesson 5: 2.5 Lewis Diagrams
Duration of Days: 1
Lesson Objective
Represent the molecular structure of a covalent compound or polyatomic ion using a Lewis diagram.
What are the mandatory rules for distributing valence electrons to ensure a stable Lewis structure?
Which elements strictly adhere to the octet rule, which are stable with an incomplete octet, and which can expand their octets into the d-subshell?
Valence Electrons
Lone Pair
Bonding Pair
Octet Rule
Duet Rule
Hypervalent
Central Atom
Learning Objective 2.5.A; Suggested Skill 3.B (Representing Data and Phenomena).
Mastery of drawing Lewis structures is a gateway skill for VSEPR and polarity. Students must account for total valence electrons, build single bonds, distribute lone pairs to terminal atoms first, and form multiple bonds if the central atom lacks an octet. Elements in Period 3 and below can exceed 8 electrons.
Support: Implement a structural checklist tally box for every molecule:
[ ] Count total valence electrons
[ ] Draw skeleton
[ ] Satisfy outer octets
[ ] Put leftovers on center
[ ] Check center octet.
Extension: Have students draw Lewis diagrams for complex hypervalent species like XeF4 or I3-, emphasizing that leftover electron pairs always sit on the central atom.
Draw the complete Lewis electron-dot diagram for the polyatomic nitrite ion, NO2^-1. Show all bonding pairs and lone pairs of electrons clearly, and include appropriate brackets and charges.