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Science lesson plan · 9th grade (Year 10 in England) · 30 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 · 4 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 magnesium is written ²⁴₁₂Mg (mass number 24, atomic number 12). How many neutrons does it have? → 12Prompt: Atomic number = number of protons (= electrons in a neutral atom).
  2. Uranium has atomic number 92. How many neutrons are in the isotope uranium-235? → 143Prompt: The number after the name is the mass number.
  3. Which number is the same for all isotopes of an element? (the number of neutrons / the relative mass / the mass number / the atomic number) → the atomic numberPrompt: Isotopes differ only in their neutrons.

Hook · 3 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 · 7 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 · 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.
  1. How many electrons does an atom of argon (atomic number 18) have in its outer shell? → 8Prompt: Fill the shells 2, 8, 8 in order.
  2. Who arranged the elements in an early periodic table and left gaps for undiscovered elements? (Isaac Newton / Dmitri Mendeleev / Marie Curie / Charles Darwin) → Dmitri MendeleevPrompt: He predicted the properties of gallium and germanium before they were found.

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.
  1. Why do elements in the same group react in similar ways? (They have the same number of electrons in their outer shell / They have the same number of neutrons / They have the same mass / They were discovered at the same time) → They have the same number of electrons in their outer shellPrompt: Reactions involve the outer electrons.
  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/ 6

  1. Question 1

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

    Answer

  2. Question 2

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

    ++++++++O

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

    • A. 8
    • B. 2,2,4
    • C. 2,6
    • D. 2,7

  3. Question 3

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

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

  4. Question 4

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

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

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

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

  5. Question 5

    Why does potassium react more vigorously with water than sodium?

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

  6. Question 6

    How many electrons does an atom of argon (atomic number 18) have in its outer shell?

    Answer

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Answer key: Electron shells and the periodic table

  1. 1. 5

  2. 2. C. 2,6

  3. 3. C. They have the same number of electrons in their outer shell

  4. 4. A. 2,8,2

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

  6. 6. 8