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S4 Chemistry: Atomic Structure and the Periodic Table – Foundation Practice (10 Questions)
S4 Chemistry: Atomic Structure and the Periodic Table – Foundation Practice (10 Questions)
Ten items start with proton, neutron and electron counts, then follow how ionic charge changes electrons, and finish with period and group from the electron arrangement.
Quick answer 1. 11 protons, 12 neutrons, 11 electrons; 2. 17, 18 and 17; 3. 12, 12 and 10; 4. 8, 8 and 10; 5. period 3, group 1; 6. period 2, group 6, gaining 2 electrons; 7. 17 protons each, with 18 and 20 neutrons; 8. 35.5; 9. period 3, group 7, ion arrangement 2, 8, 8; 10. the 2+ charge was ignored, so there are 10 electrons.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 questions |
| Suggested time | about 20 minutes |
| Difficulty mix | Foundation 4 · Intermediate 3 · 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 sodium atom has proton number 11 and nucleon number 23. State its numbers of protons, neutrons and electrons.
- FoundationA chlorine atom has proton number 17 and nucleon number 35. Write down its protons, neutrons and electrons.
- FoundationThe magnesium ion Mg2+ has proton number 12 and nucleon number 24. Find its protons, neutrons and electrons.
- FoundationThe oxide ion O2- has proton number 8 and nucleon number 16. Find its protons, neutrons and electrons.
- IntermediateAn element has the electron arrangement 2, 8, 1. Which period and which group is it in?
- IntermediateAn element has the electron arrangement 2, 6. State its period and group and how many electrons it gains or loses to form a stable ion.
- IntermediateChlorine has two isotopes, Cl-35 and Cl-37. Compare their protons and neutrons and say whether they are the same element.
- ChallengeNatural chlorine is 75 per cent Cl-35 and 25 per cent Cl-37. Calculate the relative atomic mass of chlorine.
- ChallengeAn element has the electron arrangement 2, 8, 7. Give its period, its group and the arrangement of its stable ion.
- Error redoA student wrote that Mg2+ has 12 electrons because its proton number is 12. Which step is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 11 protons, 12 neutrons and 11 electrons, because 23 minus 11 is 12. | In a neutral atom the electron count always equals the proton count. |
| 2 | 17 protons, 18 neutrons and 17 electrons. | The nucleon number counts protons and neutrons only, never electrons. |
| 3 | 12 protons, 12 neutrons and 10 electrons, since a 2+ charge means two electrons lost. | Ionic charge changes the electron count only; protons and neutrons stay the same. |
| 4 | 8 protons, 8 neutrons and 10 electrons, two more electrons than protons. | For a negative ion, add the charge magnitude to the proton number. |
| 5 | Period 3 and group 1: the number of shells gives the period, the outer electrons give the group. | Count the shells for the period first, then count the outer electrons for the group. |
| 6 | Period 2 and group 6. It gains 2 electrons to reach 2, 8 and forms a 2- ion. | With six outer electrons it is two short of eight, so it gains rather than loses. |
| 7 | Both have 17 protons, with 18 and 20 neutrons. Same proton number means the same element. | Subtract the proton number from the nucleon number to get the neutrons each time. |
| 8 | 35.5, from 0.75 times 35 plus 0.25 times 37. | Divide the percentages by 100 before multiplying, then add the two products. |
| 9 | Period 3, group 7, and it gains one electron to form a 1- ion with the arrangement 2, 8, 8. | Gaining an electron fills the outer shell to eight without adding a new shell. |
| 10 | The charge is ignored: Mg2+ has lost two electrons, so it has 10 electrons. | Read the charge first and adjust the electrons; only the protons follow the proton number. |
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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