Orbitals, Sub-Shells and Electron Configuration · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
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Addresses for every electron

Science · Chemistry · ages 16-17
Name ______________________   Date ____________

  1. How many orbitals sit in the p and d sub-shells?

    • One and three
    • Three and five
    • Five and seven

  2. How many electrons can one orbital hold?

    • One
    • Two
    • Four

  3. The 4s sub-shell fills before 3d.

    Circle one:   True   False

  4. What is the configuration of the iron(II) ion?

    • 1s2 2s2 2p6 3s2 3p6 4s2 3d4
    • 1s2 2s2 2p6 3s2 3p6 3d6 with empty 4s
    • 1s2 2s2 2p6 3s2 3p6 4s1 3d5

  5. What is the full configuration of iron, with 26 electrons?

    • 1s2 2s2 2p6 3s2 3p6 4s2 3d6
    • 1s2 2s2 2p6 3s2 3p6 3d8
    • 1s2 2s2 2p6 3s2 3p6 4s2 4p6

  6. Why is copper 4s1 3d10 instead of 4s2 3d9?

    • Copper holds 30 electrons
    • 4s can hold three electrons
    • A full d set is extra stable

  7. An element sits in the d block of period 4. Which sub-shell is filling across its row?

    • 4s
    • 4p
    • 3d

  8. A student draws oxygen 2p as two pairs. What is wrong?

    • Boxes fill singly first, so oxygen 2p is one pair plus two singles
    • Oxygen has no p electrons
    • Pairs are never allowed
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Addresses for every electron W1-mt_sRMo1f5PfJ-s1

  1. Three and five · Three boxes for p, five for d.
  2. Two · Every orbital fits at most two.
  3. True · At that point 4s sits lower in energy.
  4. 1s2 2s2 2p6 3s2 3p6 3d6 with empty 4s · Both 4s electrons leave first, leaving 3d6.
  5. 1s2 2s2 2p6 3s2 3p6 4s2 3d6 · Fill in order to 26 and 4s lands before 3d.
  6. A full d set is extra stable · One shifted electron completes the d set.
  7. 3d · The middle ten columns fill the 3d seats.
  8. Boxes fill singly first, so oxygen 2p is one pair plus two singles · Each box takes one arrow before any pairing starts.
Worksheet · LightMySky