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Science lesson plan · 9th grade (Year 10 in England) · 45 minutes

Predict ion charges from the periodic table

Atoms, elements and the periodic table

CCSS NGSS.HS-PS1-1CCSS NGSS.HS-PS1-2England: GCSE Combined Science: Bonding, structure and the properties of matter

Objective and success criteria

Students will: Predict ion charges from the periodic table.

  • 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: Electron shells and the periodic table

Leads to: Build ionic formulae from ion charges

Materials: Periodic tables, Atom model kits, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 5 min

  • Quick retrieval from earlier learning (Electron shells and the periodic table). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. How many electrons does an atom of silicon (atomic number 14) have in its outer shell? → 4Prompt: Fill the shells 2, 8, 8 in order.
  2. Who arranged the elements in an early periodic table and left gaps for undiscovered elements? (Marie Curie / Dmitri Mendeleev / Isaac Newton / Charles Darwin) → Dmitri MendeleevPrompt: He predicted the properties of gallium and germanium before they were found.
  3. How many electrons does an atom of phosphorus (atomic number 15) have in its outer shell? → 5Prompt: Fill the shells 2, 8, 8 in order.

Hook · 5 min

  • Show the periodic table and ask what patterns students can see before anything is explained.
  • Share the objective: Predict ion charges from the periodic table. Read the success criteria together.

I do: model it · 10 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Phosphorus (P) is in group 15 (5). What charge does its ion have?
  • Step 1: It gains 3 electrons, so the ion is negative.
  • Step 2: So the answer is: 3−
  • Answer: 3−
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 10 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. Aluminium (Al) is in group 13 (3). What charge does its ion have? (1− / 2− / 3− / 3+) → 3+Prompt: Metals lose their outer electrons; non-metals gain electrons to fill their outer shell.
  2. An atom of phosphorus (atomic number 15) forms its usual ion (charge 3−). How many electrons does the ion have? → 18Prompt: A neutral atom has as many electrons as protons.

You do: independent practice · 10 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 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 5 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Why do sodium and chloride ions both end up with the electron arrangement 2,8? (They both gain electrons / Sodium loses one electron and chlorine gains one, both reaching a full outer shell / They share electrons / Sodium gains seven electrons) → Sodium loses one electron and chlorine gains one, both reaching a full outer shellPrompt: Na is 2,8,1 and Cl is 2,8,7.
  2. An atom of lithium (atomic number 3) forms its usual ion (charge 1+). How many electrons does the ion have? → 2Prompt: A neutral atom has as many electrons as protons.

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: Electron shells and 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: Build ionic formulae from ion charges.
  • 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

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Predict ion charges from the periodic table

Name

Date

Score/ 8

  1. Question 1

    An atom of potassium (atomic number 19) forms its usual ion (charge 1+). How many electrons does the ion have?

    Answer

  2. Question 2

    Sodium (Na) is in group 1. What charge does its ion have?

    • A. 2−
    • B. 1+
    • C. 3−
    • D. 1−

  3. Question 3

    Why does magnesium oxide have a much higher melting point than sodium chloride?

    • A. Sodium chloride has no bonds
    • B. Magnesium oxide is covalent
    • C. Mg²⁺ and O²⁻ have larger charges, so the ionic bonds are stronger
    • D. Oxygen is a gas

  4. Question 4

    An atom of oxygen (atomic number 8) forms its usual ion (charge 2−). How many electrons does the ion have?

    Answer

  5. Question 5

    Magnesium (Mg) is in group 2. What charge does its ion have?

    • A. 3+
    • B. 3−
    • C. 2+
    • D. 1−

  6. Question 6

    What holds the ions together in sodium chloride?

    • A. strong electrostatic attraction between oppositely charged ions
    • B. weak forces between molecules
    • C. a sea of delocalised electrons
    • D. shared pairs of electrons

  7. Question 7

    An atom of lithium (atomic number 3) forms its usual ion (charge 1+). How many electrons does the ion have?

    Answer

  8. Question 8

    Nitrogen (N) is in group 15 (5). What charge does its ion have?

    • A. 2−
    • B. 3+
    • C. 2+
    • D. 3−

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Answer key: Predict ion charges from the periodic table

  1. 1. 18

  2. 2. B. 1+

  3. 3. C. Mg²⁺ and O²⁻ have larger charges, so the ionic bonds are stronger

  4. 4. 10

  5. 5. C. 2+

  6. 6. A. strong electrostatic attraction between oppositely charged ions

  7. 7. 2

  8. 8. D. 3−