Science lesson plan · 9th grade (Year 10 in England) · 30 minutes
Build ionic formulae from ion charges
Atoms, elements and the periodic table
CCSS NGSS.HS-PS1-2England: GCSE Combined Science: Bonding, structure and the properties of matter
Objective and success criteria
Students will: Build ionic formulae from ion charges.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Predict ion charges from the periodic table; Chemical formulae
Leads to: Predict the products of electrolysis
Materials: Periodic tables, Atom model kits, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).
Warm-up · 4 min
- Quick retrieval from earlier learning (Predict ion charges from the periodic table; Chemical formulae). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Sulfur (S) is in group 16 (6). What charge does its ion have? (3+ / 2+ / 3− / 2−) → 2−Prompt: Metals lose their outer electrons; non-metals gain electrons to fill their outer shell.
- How many atoms in total are in one molecule (formula unit) of sodium chloride, NaCl? → 2Prompt: A small number after a symbol tells you how many of that atom.
- An atom of nitrogen (atomic number 7) forms its usual ion (charge 3−). How many electrons does the ion have? → 10Prompt: A neutral atom has as many electrons as protons.
Hook · 3 min
- Show the periodic table and ask what patterns students can see before anything is explained.
- Share the objective: Build ionic formulae from ion charges. Read the success criteria together.
I do: model it · 7 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: What is the formula of potassium sulfate? (Ions: K⁺ and SO₄²⁻)
- Step 1: 2 × (+1) and 1 × (−2) give zero overall charge.
- Step 2: So the answer is: K₂SO₄
- Answer: K₂SO₄
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 6 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- What is the formula of magnesium oxide? (Ions: Mg²⁺ and O²⁻) (Mg₂O / MgO₂ / MgO) → MgOPrompt: The total positive charge must equal the total negative charge.
- In Ca(NO₃)₂ (calcium nitrate), how many nitrate ions are there for each formula unit? → 2Prompt: Look at the small number after the symbol or bracket.
You do: independent practice · 7 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 6 questions are on the student sheet below, with answers in the key.
Exit ticket · 3 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- What is the formula of potassium bromide? (Ions: K⁺ and Br⁻) (KBr / KBr₂ / K₂Br) → KBrPrompt: The total positive charge must equal the total negative charge.
- What is the overall charge of any ionic compound? (the charge of the metal ion / always negative / zero / always positive) → zeroPrompt: The positive and negative charges cancel.
Watch out for
- Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
- Remembering facts without the reason: ask "why?" and "what is the evidence?"
Support and stretch
Support
- Review first: Predict ion charges from the periodic table.
- Use concrete materials: periodic tables.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Move on to: Predict the products of electrolysis.
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-9.
Free lesson plan from eurekami.com/lesson-plan-builder