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Science lesson plan · 9th grade (Year 10 in England) · 45 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 · 5 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 oxygen is written ¹⁶₈O (mass number 16, atomic number 8). How many neutrons does it have? → 8Prompt: Atomic number = number of protons (= electrons in a neutral atom).
  2. Oxygen has atomic number 8. How many neutrons are in the isotope oxygen-16? → 8Prompt: 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 / +1 / +11 / 0) → +1Prompt: It now has one more proton than electrons.

Hook · 5 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 · 10 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 · 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. How many electrons does an atom of fluorine (atomic number 9) have in its outer shell? → 7Prompt: Fill the shells 2, 8, 8 in order.
  2. Why do elements in the same group react in similar ways? (They have the same mass / They have the same number of electrons in their outer shell / They have the same number of neutrons / They were discovered at the same time) → They have the same number of electrons in their outer shellPrompt: Reactions involve the outer electrons.

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. Who arranged the elements in an early periodic table and left gaps for undiscovered elements? (Dmitri Mendeleev / Marie Curie / Charles Darwin / Isaac Newton) → Dmitri MendeleevPrompt: He predicted the properties of gallium and germanium before they were found.
  2. How many electrons does an atom of calcium (atomic number 20) have in its outer shell? → 2Prompt: 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

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

    Answer

  2. Question 2

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

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

  3. Question 3

    Oxygen has atomic number 8. What is its electronic structure?

    ++++++++O

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

    • A. 1,7
    • B. 8
    • C. 2,7
    • D. 2,6

  4. Question 4

    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 is a non-metal
    • C. It has fewer protons
    • D. It has a full outer shell

  5. Question 5

    Argon has atomic number 18. What is its electronic structure?

    18 p22 nAr

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

    • A. 2,2,14
    • B. 2,16
    • C. 18
    • D. 2,8,8

  6. Question 6

    How many electrons does an atom of calcium (atomic number 20) have in its outer shell?

    Answer

  7. Question 7

    Why do elements in the same group react in similar ways?

    • A. They were discovered at the same time
    • B. They have the same number of electrons in their outer shell
    • C. They have the same number of neutrons
    • D. They have the same mass

  8. Question 8

    Nitrogen has atomic number 7. What is its electronic structure?

    +++++++N

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

    • A. 2,6
    • B. 1,6
    • C. 2,5
    • D. 2,2,3

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Answer key: Electron shells and the periodic table

  1. 1. 5

  2. 2. C. Dmitri Mendeleev

  3. 3. D. 2,6

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

  5. 5. D. 2,8,8

  6. 6. 2

  7. 7. B. They have the same number of electrons in their outer shell

  8. 8. C. 2,5