Molecular Orbital Theory for Homonuclear Diatomics · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Two atoms sharing whole orbitals

Science · Chemistry · ages 18-19
Name ______________________   Date ____________

  1. How is bond order calculated from electron counts?

    • Bonding plus antibonding, halved
    • Bonding minus antibonding, halved
    • Bonding times antibonding, halved

  2. Two atomic orbitals combine. Where does the bonding orbital land?

    • The bonding combination sits lower than the parents
    • Both combinations sit at the parent energy
    • The antibonding combination sits lowest of all

  3. The antibonding orbital sits above the parents by more than the bonding orbital sits below them.

    Circle one:   True   False

  4. Which filling order applies to nitrogen and to oxygen?

    • The unmixed order for both
    • The mixed order for both
    • Mixed for nitrogen, unmixed for oxygen

  5. A diatomic has 8 bonding and 2 antibonding electrons. What is its bond order?

    Answer: ______________

  6. What does a higher bond order mean for the bond?

    • Longer, weaker, easier to break
    • Unchanged, since order is only bookkeeping
    • Shorter, stronger, harder to break

  7. A student draws the boron diagram with the pz sigma below the pi pair. What is the error?

    • It skipped the s p mixing, so its ladder order is wrong
    • It used too few electrons overall
    • It paired electrons that must stay parallel

  8. Liquid oxygen sticks to a magnet, yet its Lewis structure shows all electrons paired. How does the orbital diagram resolve this?

    • Oxygen has no unpaired electrons at all
    • Oxygen carries two unpaired electrons
    • Oxygen is a permanent magnet
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Answer key

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

Two atoms sharing whole orbitals W1-mt_wRBDDmRYka-s1

  1. Bonding minus antibonding, halved · That single number predicts strength, length, and magnetism.
  2. The bonding combination sits lower than the parents · Adding waves between nuclei stabilises, cancelling destabilises.
  3. True · The upward push always outweighs the downward drop.
  4. Mixed for nitrogen, unmixed for oxygen · Close 2s and 2p levels mix before oxygen, then the gap widens.
  5. 3 · Eight minus two is six, and half of six is three.
  6. Shorter, stronger, harder to break · Nitrogen with its triple bond is short and stubborn, fluorine with its single bond is long and weak.
  7. It skipped the s p mixing, so its ladder order is wrong · Diagrams before oxygen need the mixed order or they mislead.
  8. Oxygen carries two unpaired electrons · The shared pair picture pairs everything, but the magnet disagrees.
Worksheet · LightMySky