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Science lesson plan · 9th grade (Year 10 in England) · 60 minutes

Electron shells and the periodic table

Atoms, elements and the periodic table

CCSS NGSS.HS-PS1-1England: KS4 Combined Science: Atomic structure and the periodic table

Objective and success criteria

Students will: Electron shells and 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: Atomic number, mass number and isotopes

Leads to: Ionic, covalent and metallic bonding; Predict ion charges from the periodic table

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

Warm-up · 6 min

  • Quick retrieval from earlier learning (Atomic number, mass number and isotopes). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. An atom of lithium is written ⁷₃Li (mass number 7, atomic number 3). How many neutrons does it have? → 4Prompt: Atomic number = number of protons (= electrons in a neutral atom).
  2. Chlorine has atomic number 17. How many neutrons are in the isotope chlorine-35? → 18Prompt: The number after the name is the mass number.
  3. Which number is the same for all isotopes of an element? (the mass number / the number of neutrons / the relative mass / the atomic number) → the atomic numberPrompt: Isotopes differ only in their neutrons.

Hook · 6 min

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

I do: model it · 12 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: How many electrons does an atom of neon (atomic number 10) have in its outer shell?
  • Step 1: 2,8
  • Step 2: So the answer is: 8
  • Answer: 8
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 12 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. How many electrons does an atom of nitrogen (atomic number 7) have in its outer shell? → 5Prompt: Fill the shells 2, 8, 8 in order.
  2. Why are noble gases so unreactive? (They are very heavy / Their outer shell is full / They have no electrons / They are liquids) → Their outer shell is fullPrompt: Atoms react to gain a full outer shell.

You do: independent practice · 17 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 · 7 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. How many electrons does an atom of lithium (atomic number 3) have in its outer shell? → 1Prompt: Fill the shells 2, 8, 8 in order.
  2. Why does potassium react more vigorously with water than sodium? (It is a non-metal / Its outer electron is further from the nucleus, so it is lost more easily / It has fewer protons / It has a full outer shell) → Its outer electron is further from the nucleus, so it is lost more easilyPrompt: Potassium has one more shell than sodium.

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: Atomic number, mass number and isotopes.
  • 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: Ionic, covalent and metallic bonding; Predict ion charges from the periodic table.
  • 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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Electron shells and the periodic table

Name

Date

Score/ 8

  1. Question 1

    Why are noble gases so unreactive?

    • A. Their outer shell is full
    • B. They are liquids
    • C. They are very heavy
    • D. They have no electrons

  2. Question 2

    Magnesium has atomic number 12. What is its electronic structure?

    ++++++++++++Mg

    coral + = proton · grey = neutron · purple − = electron

    • A. 12
    • B. 2,8,3
    • C. 2,2,8
    • D. 2,8,2

  3. Question 3

    How many electrons does an atom of potassium (atomic number 19) have in its outer shell?

    Answer

  4. Question 4

    Why does potassium react more vigorously with water than sodium?

    • A. It has a full outer shell
    • B. It has fewer protons
    • C. It is a non-metal
    • D. Its outer electron is further from the nucleus, so it is lost more easily

  5. Question 5

    Sodium has atomic number 11. What is its electronic structure?

    +++++++++++Na

    coral + = proton · grey = neutron · purple − = electron

    • A. 2,9
    • B. 2,8,1
    • C. 11
    • D. 2,8,2

  6. Question 6

    How many electrons does an atom of phosphorus (atomic number 15) have in its outer shell?

    Answer

  7. Question 7

    Who arranged the elements in an early periodic table and left gaps for undiscovered elements?

    • A. Dmitri Mendeleev
    • B. Isaac Newton
    • C. Marie Curie
    • D. Charles Darwin

  8. Question 8

    Lithium has atomic number 3. What is its electronic structure?

    +++Li

    coral + = proton · grey = neutron · purple − = electron

    • A. 1,2
    • B. 2,1
    • C. 2,2
    • D. 3

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Answer key: Electron shells and the periodic table

  1. 1. A. Their outer shell is full

  2. 2. D. 2,8,2

  3. 3. 1

  4. 4. D. Its outer electron is further from the nucleus, so it is lost more easily

  5. 5. B. 2,8,1

  6. 6. 5

  7. 7. A. Dmitri Mendeleev

  8. 8. B. 2,1