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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 sodium is written ²³₁₁Na (mass number 23, atomic number 11). How many neutrons does it have? → 12Prompt: Atomic number = number of protons (= electrons in a neutral atom).
  2. Carbon has atomic number 6. How many neutrons are in the isotope carbon-12? → 6Prompt: The number after the name is the mass number.
  3. A sodium atom loses one electron to become a sodium ion. What is its charge? (+1 / +11 / 0 / −1) → +1Prompt: It now has one more proton than electrons.

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 silicon (atomic number 14) have in its outer shell? → 4Prompt: Fill the shells 2, 8, 8 in order.
  2. Why are noble gases so unreactive? (They are very heavy / They have no electrons / Their outer shell is full / 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. Why are noble gases so unreactive? (Their outer shell is full / They are liquids / They have no electrons / They are very heavy) → Their outer shell is fullPrompt: Atoms react to gain a full outer shell.
  2. How many electrons does an atom of potassium (atomic number 19) have in its outer shell? → 1Prompt: Fill the shells 2, 8, 8 in order.

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

    Silicon has atomic number 14. What is its electronic structure?

    ++++++++++++++Si

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

    • A. 2,2,10
    • B. 2,8,4
    • C. 2,12
    • D. 2,8,5

  2. Question 2

    Why are noble gases so unreactive?

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

  3. Question 3

    How many electrons does an atom of nitrogen (atomic number 7) have in its outer shell?

    Answer

  4. Question 4

    Potassium has atomic number 19. What is its electronic structure?

    19 p20 nK

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

    • A. 2,8,8,2
    • B. 2,17
    • C. 2,8,8,1
    • D. 19

  5. Question 5

    Why does potassium react more vigorously with water than sodium?

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

  6. Question 6

    How many electrons does an atom of sodium (atomic number 11) have in its outer shell?

    Answer

  7. Question 7

    Boron has atomic number 5. What is its electronic structure?

    +++++B

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

    • A. 2,4
    • B. 2,3
    • C. 2,2,1
    • D. 5

  8. Question 8

    How many electrons does an atom of boron (atomic number 5) have in its outer shell?

    Answer

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Answer key: Electron shells and the periodic table

  1. 1. B. 2,8,4

  2. 2. C. Their outer shell is full

  3. 3. 5

  4. 4. C. 2,8,8,1

  5. 5. A. Its outer electron is further from the nucleus, so it is lost more easily

  6. 6. 1

  7. 7. B. 2,3

  8. 8. 3