Question 1Multiple choice · 1 markA* challenge
How many protons, neutrons and electrons are there in the ion 3919K+?
| protons | neutrons | electrons | |
|---|---|---|---|
| A | 19 | 20 | 20 |
| B | 19 | 20 | 18 |
| C | 18 | 20 | 19 |
| D | 19 | 39 | 18 |
Show answer
Answer: B
Free Atomic structure & the Periodic Table questions for IGCSE Chemistry (0620), part of Atoms, elements & compounds. Each question has the answer and the marking points an examiner would look for.
Generate a full Atomic Structure & the Periodic Table worksheet →All Atoms, elements & compounds questionsHow many protons, neutrons and electrons are there in the ion 3919K+?
| protons | neutrons | electrons | |
|---|---|---|---|
| A | 19 | 20 | 20 |
| B | 19 | 20 | 18 |
| C | 18 | 20 | 19 |
| D | 19 | 39 | 18 |
Answer: B
Which particle has a relative charge of −1 and a very small mass?
Answer: A
Magnesium has atomic number 12.
Draw/describe the electron arrangement of a magnesium atom.
Describe how the electronic configuration of magnesium changes when it forms an ion, and give the charge on the ion.
Explain why the noble gases are unreactive in terms of electronic configuration.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 2,8,2 2,8,2 B1 | 1 |
| (b) | loses 2 outer electrons; 2+ loses its two outer electrons to become 2,8 B1 forms Mg²⁺ B1 | 2 |
| (c) | full outer shell they have a full outer shell of electrons B1 | 1 |
Complete Table 4.1.
| particle | number of protons | number of neutrons | number of electrons |
|---|---|---|---|
| carbon atom (atomic number 6, mass number 12) | |||
| F− ion (atomic number 9, mass number 19) |
Fig. 4.1 shows the electronic structure of an atom of element X.
Identify element X and state its group and period.
Define the term isotopes.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | atom: 6, 6, 6; ion: 9, 10, 10 Atom row correct B1 Ion protons and neutrons correct B1 Ion electrons = 10 B1 | 3 |
| (b) | calcium; Group 2; Period 4 calcium B1 Group 2 B1 Period 4 B1 | 3 |
| (c) | Atoms of the same element with the same number of protons but different numbers of neutrons same number of protons / same element B1 different numbers of neutrons B1 | 2 |
The Periodic Table is arranged in periods and groups.
State how the period number of an element relates to its electronic configuration.
An element has the electronic configuration 2,8,3. Identify the element and its group.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | number of occupied shells the period number equals the number of occupied electron shells B1 | 1 |
| (b) | aluminium, Group III aluminium B1 Group III B1 | 2 |
Protons, neutrons and electrons are the subatomic particles.
Complete the relative charge and relative mass of each particle.
Explain why atoms are electrically neutral.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | p +1, 1; n 0, 1; e −1, 1/1836 proton: +1, 1 B1 neutron: 0, 1 B1 electron: −1, 1/1836 (negligible) B1 | 3 |
| (b) | equal protons and electrons they have equal numbers of protons and electrons B1 | 1 |
Riyaz Shaikh has mentored IGCSE, IB and A Level students for 15+ years, one-on-one, online and in Mumbai. The hardest questions on this site are the ones he uses to find a student's weak points.
Meet Riyaz →Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in