Enhanced overlay: Weeks 1-2 bootcamp session-07.html may be taught with this lesson. The bootcamp is not the whole course.

Canonical lesson CHEMISTRY20-U1-L18 · outcome 20-A2.5k · depth ENHANCED_BOOTCAMP_OVERLAY

Unit A: Diversity of Matter and Chemical Bonding - outcome 20-A2.5k

• Course: CHEMISTRY20 (SCN2796)
• Lesson ID: CHEMISTRY20-U1-L18
• Official outcome: 20-A2.5k (KNOWLEDGE)
• Object type: canonical lesson (not a bootcamp session)
• Source: Alberta Chemistry 20 Program of Studies (2007, updated 2014)

Official outcome text

apply VSEPR theory to predict molecular shapes for linear, angular (V-shaped, bent), tetrahedral, trigonal pyramidal and trigonal planar molecules

Learning intention

Meet 20-A2.5k with instruction, practice, and a check. The 10-session bootcamp does not replace this lesson.

Success criteria

1. Restate the outcome in classroom language without swapping in a different unit’s template.
2. Complete the worked-style task for this outcome.
3. Name the lab setting (classroom-supervised / teacher demo / dataset or simulation / forbidden).

Teaching

VSEPR: electron groups (bonds and lone pairs) repel and occupy positions as far apart as possible. Two groups: linear (180°, CO2). Three groups, no lone pairs: trigonal planar (BF3). Three groups with one lone pair: angular/bent (SO2 class). Four groups, no lone pairs: tetrahedral (CH4). Three bonds + one lone pair: trigonal pyramidal (NH3). Two bonds + two lone pairs: angular/bent (H2O).

Worked example

CH4 tetrahedral; NH3 trigonal pyramidal (lone pair occupies more space); H2O bent; CO2 linear even though it has two double bonds (two electron groups).

Guided practice

1. Predict the shape of SO2 (treat S with a lone pair; bent) vs CO2 (linear). Do not copy CH4/NH3/H2O only.
2. Near-miss: CO2 called bent because it has two oxygens. Mark the first wrong line.

Independent practice

1. Shapes: BF3, PF3, SiH4.
2. Two sentences: electron groups vs bonded atoms in NH3.
3. Name the five required VSEPR shapes from the outcome.

Diagram / whiteboard

Approved diagram id chem20-ionic-lattice - Ionic lattice / bonding sketch. Tutor may open the course whiteboard and display this id. Do not invent hazardous procedures on the board.

Checks for understanding

Use the formative evidence below as the exit check for this outcome. Correct the misconception named in this lesson before praising.

Misconception to repair

Predicting H2O as tetrahedral molecular shape because there are four electron groups - the molecular shape names the atom positions, not the electron-group geometry.

Safety and lab register

Setting: classroom-supervised only for Session 04 conductivity (NaCl / sucrose / ~5% vinegar, 9 V LED or school probe). All other Unit A work is paper, models, data cards, or approved simulation. Forbidden: bleach+acid, bleach+ammonia, flames, tasting, home copy of Session 04, concentrated acids/bases, generating Cl2. AI Tutor must not invent labs outside CHEM20_LOW_RESOURCE_LAB_REGISTER.csv.

Alberta Poison Control if a real exposure is occurring: 1-844-764-7669. The AI Tutor is not a poison centre.

Formative evidence

Table of CH4, NH3, H2O, CO2, BF3 with electron groups and shape names.

This is not a diploma. Mastery needs instruction + activity + check.

AI Tutor / human tutor

Ground on 20-A2.5k. No false praise. No invented procedures. No silent skip to a different unit. Human tutor if the student describes mixing bleach, tasting, or flames.

Provenance

Official POS wording from ALBERTA_SENIOR_HIGH_OFFICIAL_OUTCOMES.csv. Pack lesson written to replace Wave-4 contaminated canonical markdown.