Main-Group Chemistry: What Changes Down a p-Block Group · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

What changes as you go down a p-block group

Science · Chemistry · ages 19-20
Name ______________________   Date ____________

  1. Why do nitrogen and phosphorus, both in group 15, have similarities in their chemistry?

    • They have equal numbers of protons in their nuclei
    • They have equal atomic sizes and identical bond energies
    • They have equal valence-electron counts

  2. A neutral atom is in group 15. How many valence electrons does it have?

    • Five
    • Three
    • Eight

  3. The usual Lewis structure of BF3 has three B-F single bonds and no lone pair on boron, giving six electrons around boron.

    Circle one:   True   False

  4. Lead has oxidation state +2 in PbO and +4 in PbO2. How much lower is its oxidation state in PbO? Enter the difference.

    Answer: ______________

  5. A Lewis structure of SF6 has six S-F single bonds and no sulfur lone pairs. How many electrons are counted around sulfur?

    • 6 electrons, counting one from each of the six bonds
    • 12 electrons, counting two from each of the six bonds
    • 8 electrons, because every central atom must have an octet

  6. Which thallium oxidation state is commonly favoured over Tl(III) by the inert-pair effect?

    • Tl(I)
    • Tl(III)
    • Tl(V)

  7. Compare NH3 with BiH3, and acidic N2O5 with Bi2O3. Which statement matches the taught group 15 comparisons?

    • Bi-H bonds are generally stronger; Bi2O3 is acidic like N2O5
    • Bi-H bonds are generally weaker; Bi2O3 is basic
    • N-H and Bi-H bonds have equal strength; both oxides are neutral

  8. Lee draws seven two-electron C-Cl single bonds at carbon in an ordinary octet-based Lewis structure. What is the counting error?

    • The seven single bonds count only seven electrons, leaving carbon below eight
    • Carbon has seven valence electrons, so each chlorine bond must be ionic
    • The fourteen-electron count exceeds carbon's ordinary Lewis octet
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Answer key

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What changes as you go down a p-block group W1-mt_wq15-pBrI5-s1

  1. They have equal valence-electron counts · Each neutral atom has five valence electrons. This helps explain similarities without making their sizes or reactions identical.
  2. Five · For groups 13 to 18, subtract ten. Here, 15 - 10 = 5 valence electrons.
  3. True · Three single bonds contribute three pairs: 3 × 2 = 6. BF3 is an example of an incomplete octet.
  4. 2 · The difference is 4 - 2 = 2. These are formal oxidation states, not measurements of actual electron loss.
  5. 12 electrons, counting two from each of the six bonds · Each single bond contributes two electrons to the Lewis count at sulfur. Six bonds give 6 × 2 = 12.
  6. Tl(I) · Tl(I) is the commonly favoured lower state in this comparison. The numeral gives oxidation state, not a required number of bonds.
  7. Bi-H bonds are generally weaker; Bi2O3 is basic · The larger bismuth atom overlaps less effectively with H 1s, giving weaker Bi-H bonds. Bi2O3 is basic, whereas N2O5 is acidic.
  8. The fourteen-electron count exceeds carbon's ordinary Lewis octet · Seven shared pairs count fourteen electrons around carbon. That exceeds the eight-electron limit of the stated Lewis model.
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