Enhanced overlay: Weeks 1-2 bootcamp session-02.html may be taught with this lesson. The bootcamp is not the whole course.

Canonical lesson CHEMISTRY20-U1-L02 · outcome 20-A1.2k · depth ENHANCED_BOOTCAMP_OVERLAY

Unit A: Diversity of Matter and Chemical Bonding - outcome 20-A1.2k

• Course: CHEMISTRY20 (SCN2796)
• Lesson ID: CHEMISTRY20-U1-L02
• Official outcome: 20-A1.2k (KNOWLEDGE)
• Object type: canonical lesson (not a bootcamp session)
• Source: Alberta Chemistry 20 Program of Studies (2007, updated 2014)

Official outcome text

explain why formulas for ionic compounds refer to the simplest whole-number ratio of ions that result in a net charge of zero

Learning intention

Meet 20-A1.2k 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

An ionic formula is an empirical formula: the smallest whole-number ratio of ions that makes the crystal electrically neutral. Mg2+ and Cl− combine as MgCl2, not MgCl, because one +2 ion needs two −1 ions. The crystal contains huge numbers of ions; the formula does not mean “one molecule of MgCl2.”

Worked example

Al3+ with O2−: least common multiple of charges is 6, so Al2O3. Check: 2(+3)+3(−2)=0. Na+ with CO32−: Na2CO3, not NaCO3.

Guided practice

1. Write the empirical ionic formula for Mg2+ with N3−. Show the LCM of charges and the zero-sum check. Do not copy Al2O3.
2. Near-miss: a student writes Na2Cl2 “because two ions.” Mark the first wrong line.

Independent practice

1. Formula for Fe3+ with O2−, with the arithmetic check.
2. Two sentences: why ionic formulas are empirical ratios, not molecule counts.
3. Reject or accept Ca3N2 vs CaN2 with a charge check.

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

Writing molecular-style formulas (Na2Cl2) or thinking the formula counts molecules of an ionic compound.

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

Write Al2O3 from ions and one sentence on why Na2Cl2 is not used.

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

AI Tutor / human tutor

Ground on 20-A1.2k. 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.