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S4 Chemistry: The Periodic Table — Practice Paper 3 (10 Questions)
S4 Chemistry: The Periodic Table — Practice Paper 3 (10 Questions)
Paper 3 links the table to the mole and to mass fractions: working back to atomic number, converting moles to mass, finding an empirical formula, and redoing the atomic-number error.
Quick answer Ten questions, about 25 minutes. Items 01, 05 and 08 place elements from arrangement or atomic number; 02, 03 and 09 are mole and mass calculations; 04 finds an empirical formula; 06 and 07 compare ionisation energy and isoelectronic species; item 10 redoes atomic number as mass number.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 questions |
| Suggested time | 25 minutes |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: Secondary 4 Maths: Equivalent Fractions and Decimals — Tutor Lesson Plan |
| Level | Secondary 4 |
02 Questions (10 items)
- FoundationAn element has arrangement 2, 8, 6. Give its atomic number, position and the ion it forms.
- FoundationWhat is the mass of 1 mol of sodium, and how many atoms does it hold?
- Foundation3.01×10²³ magnesium atoms weigh how much? (Mg 24)
- FoundationA compound is 40% calcium, 12% carbon and 48% oxygen by mass. Find the empirical formula.
- IntermediateElements with atomic numbers 19 and 17 react. What compound forms?
- IntermediateFirst ionisation energies: lithium 520, sodium 494, potassium 419 kJ/mol. Order them and explain.
- IntermediateDo argon (Z = 18) and the potassium ion K⁺ (Z = 19) hold the same number of electrons?
- ChallengePredict the position of the element with atomic number 35.
- ChallengeHow much calcium is in 20 g of calcium carbonate? (Ca 40, CaCO₃ 100)
- Error redoError drill: why is treating atomic number as mass number wrong (Z = 17, mass 35 for chlorine)?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Z = 16 (sulfur), Period 3 Group VI, gaining two electrons to S²⁻. | 2 + 8 + 6 = 16, and six outer electrons favour gaining two. |
| 2 | 23 g, holding 6.02×10²³ atoms. | Molar mass in grams equals the relative atomic mass. |
| 3 | 0.5 mol, so 12 g. | Divide the atom count by the Avogadro constant. |
| 4 | CaCO₃. | 40/40 = 1, 12/12 = 1, 48/16 = 3, giving 1 : 1 : 3. |
| 5 | Potassium chloride, KCl. | Potassium loses one electron to K⁺; chlorine gains one to Cl⁻. |
| 6 | Potassium < sodium < lithium. | Down a group the outer electron sits further from the nucleus. |
| 7 | Yes, 18 each. | They are isoelectronic species. |
| 8 | 2, 8, 18, 7; Period 4 Group VII (bromine). | Four shells means Period 4; seven outer electrons means Group VII. |
| 9 | 20 × 40/100 = 8 g. | Use the mass fraction of calcium in the compound. |
| 10 | Neutrons are 35 minus 17, giving 18. | Atomic number counts protons only. |
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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