Unit 02 · Chemical Bonding & Molecular Geometry
Bonding is where atoms become substances. This unit covers why electrons are transferred or shared — ionic, covalent, and metallic bonding — how to draw valid Lewis structures, how VSEPR theory turns those structures into three-dimensional shapes, and how shape plus electronegativity decides whether a molecule is polar. Mastery means you can go from a formula to a shape to a prediction about the substance's behavior.
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Bond type & electronegativity | Cannot tell ionic from covalent from metallic. | Classifies bonds by element type but not by electronegativity difference. | Uses electronegativity differences to classify bonds and predict each type's properties. |
| Lewis structures | Draws structures with wrong electron counts. | Draws simple molecules but misses lone pairs, formal charge, or resonance. | Draws valid structures including resonance, expanded octets, and correct formal charges. |
| VSEPR & molecular geometry | Cannot name a molecular shape. | Names shapes from a chart without accounting for lone pairs. | Predicts shape and bond angles from electron domains, distinguishing molecular from electron geometry. |
| Polarity & intermolecular consequences | Calls every molecule with polar bonds polar. | Identifies polar bonds but ignores symmetry. | Uses geometry and dipole cancellation to determine overall polarity and predict solubility. |
| Lab technique (model building / conductivity) | Builds models that violate the structure or skips testing. | Builds correct models but cannot link them to a property test. | Builds accurate 3-D models and confirms predictions with a conductivity or solubility test. |
| Integration (cross-domain) | Treats the science as isolated facts; makes no cross-domain connection. | Names a link to history, reading, or writing but cannot defend why it matters. | Connects the unit to its anchor across History · Reading · Writing (plus chosen electives) and defends why the connection matters. |
“CO₂ is linear because carbon has two double bonds and no lone pairs, so VSEPR pushes them 180° apart. Each C=O is polar, but the two pull opposite ways and cancel, so the whole molecule comes out nonpolar.”
“It’s covalent because they share electrons. The shape is bent, maybe? Polar means it has charges somewhere.”
You demonstrate this unit by building physical molecular models and running conductivity and solubility tests, then explaining your structures aloud — not a multiple-choice test. A criterion counts as mastered only when you can both build the model and justify why the bonding produces that shape and behavior. Mastery is demonstrated, not awarded.
A 5-page clipboard packet — unit overview, key terms, the mastery rubric, anchor examples, and a score sheet you can print and grade against.