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S4 Chemistry: Atomic Structure and the Periodic Table – Advanced Practice (10 Questions)
S4 Chemistry: Atomic Structure and the Periodic Table – Advanced Practice (10 Questions)
Ten items reverse the relations: proton number from electrons, nucleon number from neutrons, then relative atomic mass from isotope abundances.
Quick answer 1. 20 neutrons and the arrangement 2, 8, 8, 1; 2. 14 neutrons, 10 electrons; 3. 20 neutrons, 18 electrons, arrangement 2, 8, 8; 4. 20.2; 5. 63.6; 6. period 3, group 6, ion with 18 electrons; 7. proton number 15, arrangement 2, 8, 5, period 3, group 5; 8. proton number 20 with 20 neutrons, calcium; 9. 24.32; 10. period is the shell count and group is the outer electron count.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 questions |
| Suggested time | about 25 minutes |
| Difficulty mix | Foundation 3 · Intermediate 4 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: S4 Chemistry | Atomic Structure and the Periodic Table: proton number, nucleon number and electron arrangement |
| Level | S4 |
02 Questions (10 items)
- FoundationA potassium atom has proton number 19 and nucleon number 39. Find its neutrons and electron arrangement.
- FoundationThe aluminium ion Al3+ has proton number 13 and nucleon number 27. Find its neutrons and electrons.
- FoundationThe calcium ion Ca2+ has proton number 20 and nucleon number 40. Find its neutrons, electrons and electron arrangement.
- IntermediateNatural neon is 90 per cent Ne-20 and 10 per cent Ne-22. Calculate its relative atomic mass.
- IntermediateNatural copper is 70 per cent Cu-63 and 30 per cent Cu-65. Calculate its relative atomic mass.
- IntermediateAn element has the electron arrangement 2, 8, 6. Give its period, group and the electron count of its stable ion.
- IntermediateAn atom has nucleon number 31 and 16 neutrons. Find its proton number, electron arrangement, period and group.
- ChallengeAn ion X2+ has 18 electrons and nucleon number 40. Find its proton number and neutrons and name the element.
- ChallengeNatural magnesium is 79 per cent Mg-24, 10 per cent Mg-25 and 11 per cent Mg-26. Calculate its relative atomic mass.
- Error redoA student swapped the labels and wrote group 3, period 1. How should period and group be told apart?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 20 neutrons, with the arrangement 2, 8, 8, 1. | Subtract for the neutrons first, then fill shells in the order 2, 8, 8. |
| 2 | 14 neutrons and 10 electrons. | A 3+ charge means three electrons lost, so 13 minus 3 is 10. |
| 3 | 20 neutrons, 18 electrons and the arrangement 2, 8, 8. | After losing the two outer electrons the fourth shell is empty, leaving three shells. |
| 4 | 20.2, from 0.90 times 20 plus 0.10 times 22. | Check that the abundances add to 100 per cent before multiplying. |
| 5 | 63.6, from 44.1 plus 19.5. | The answer must lie between 63 and 65 because the two isotopes differ by two units. |
| 6 | Period 3, group 6, and the ion has 18 electrons after gaining two. | The ion total is 16 plus 2, matching the filled arrangement 2, 8, 8. |
| 7 | Proton number 15, arrangement 2, 8, 5, period 3 and group 5. | Proton number equals nucleon number minus neutrons; everything else follows. |
| 8 | Proton number 20, 20 neutrons, so the element is calcium. | Add back the two lost electrons before reading off the proton number. |
| 9 | 24.32, from 18.96 plus 2.5 plus 2.86. | All three products must be added; missing one makes the answer too low. |
| 10 | The period is the number of shells and the group is the number of outer electrons, so 2, 8, 1 means period 3 and group 1. | State the shell count first and the outer electrons second every time. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
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