Pearson Edexcel International GCSE Chemistry 4CH1: Atomic structure and the Periodic Table – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover sub-topics 1(c) Atomic structure and 1(d) The Periodic Table (points 1.14–1.24) of the Pearson Edexcel International GCSE Chemistry (4CH1) specification, Issue 3 (September 2024). The qualification is untiered and none of these points has a “C” reference, so all of the questions suit both Paper 1 and Paper 2. A calculator may be used on both papers.

Before you start, read the atomic structure and Periodic Table study guide or the revision notes. The questions here are different from those in the Principles of chemistry practice questions, which cover the whole of Topic 1. Course links: the 4CH1 Chemistry course hub and the printable 4CH1 checklist.

Questions

1. Copy and complete the table for the three sub-atomic particles. [3]

Particle	Relative mass	Relative charge
Proton
Neutron
Electron

2. This question is about atoms and molecules.

(a) State what is meant by a molecule. [1] (b) Helium, nitrogen, ammonia and argon are all gases at room temperature. State which two of these substances are made of molecules. [1] (c) One of your answers to (b) is an element. Name it and give a reason. [1]

3. Copy and complete the table to show the numbers of protons, neutrons and electrons in each particle. [4]

Particle	Protons	Neutrons	Electrons
¹⁸₈O
⁴⁰₂₀Ca
²⁷₁₃Al³⁺
²³₁₁Na⁺

4. A sample of silicon contains 92.2% silicon-28, 4.7% silicon-29 and 3.1% silicon-30. Calculate the relative atomic mass of silicon. Give your answer to 1 decimal place. [2]

5. This question is about how the Periodic Table is arranged.

(a) State the property used to put the elements in order. [1] (b) Argon has a relative atomic mass of 39.9 and potassium has a relative atomic mass of 39.1. Explain why argon is placed before potassium in the Periodic Table. [2] (c) State what the atoms of all the elements in one period have in common. [1]

6. Give the electronic configuration of the element found in each position. [3]

(a) Period 2, Group 7 (b) Period 3, Group 3 (c) Period 4, Group 1

7. An atom of element Z has the electronic configuration 2,8,2.

(a) State the group and the period of Z. [2] (b) Name element Z. [1] (c) Name one other element with similar chemical properties to Z and explain your choice. [2]

8. A student tests four elements, W, X, Y and Z. The results are shown below.

Element	Does the solid conduct electricity?	Test on the oxide
W	Yes	Dissolves in water; universal indicator turns purple
X	No	Dissolves in water; universal indicator turns red
Y	Yes	Insoluble in water; reacts with dilute sulfuric acid to form a salt and water
Z	Yes	A gas that dissolves in water to give a solution of pH 5

(a) Classify each element as a metal or a non-metal. Give a reason for each, using the oxide result. [4] (b) Element Z is a non-metal. Suggest the identity of Z and explain why the conductivity result alone would have misled the student. [1] (c) Describe how the student could show that the oxide of Y is basic, and state the result. [2]

9. Explain each of the following in terms of electrons.

(a) Lithium and potassium have similar chemical properties. [2] (b) Neon does not readily react. [2] (c) Helium is placed in Group 0 even though its atoms have only two electrons. [1]

10. Chlorine has two isotopes, chlorine-35 and chlorine-37. Its relative atomic mass is 35.5.

(a) Calculate the percentage abundance of chlorine-35. [3] (b) Give the electronic configuration of a chlorine atom (atomic number 17). [1] (c) Explain how this configuration shows the group and the period of chlorine. [2] (d) An oxide of chlorine dissolves in water. Predict whether the solution has a pH above or below 7, and explain your prediction using the position of chlorine in the Periodic Table. [2]

11. A sample of potassium contains 93.3% potassium-39 and 6.7% potassium-41. Potassium has atomic number 19.

(a) Calculate the relative atomic mass of potassium. Give your answer to 1 decimal place. [2] (b) State the numbers of protons, neutrons and electrons in an atom of potassium-41. [2] (c) Give the electronic configuration of potassium and state its group and period. [2] (d) Describe a test on potassium oxide that shows potassium is a metal. Give the expected result. [2] (e) Explain why potassium reacts in a similar way to sodium. [2]

Answers

1. Proton: relative mass 1, relative charge +1 [1]. Neutron: relative mass 1, relative charge 0 [1]. Electron: relative mass about 1/1840 (negligible), relative charge −1 [1]. Examiner insight: each row is usually marked as a unit, so one wrong value in a row loses that row’s mark; write “0” for the neutron’s charge rather than leaving the cell blank.

2. (a) Two or more atoms chemically (covalently) bonded together [1]. (b) Nitrogen and ammonia [1]. (c) Nitrogen: its molecules contain only one type of atom (N₂) [1]. Examiner insight: “a group of atoms” without the idea of bonding is too vague for the definition mark; the word “bonded” or “joined chemically” is what earns it.

3. ¹⁸O: 8, 10, 8 [1]. ⁴⁰Ca: 20, 20, 20 [1]. ²⁷Al³⁺: 13, 14, 10 [1]. ²³Na⁺: 11, 12, 10 [1]. Examiner insight: a mark per row means one slip costs only that row; check each ion separately by subtracting the charge from the proton number, not from the mass number.

4. Ar = (28 × 92.2 + 29 × 4.7 + 30 × 3.1) ÷ 100 = (2581.6 + 136.3 + 93.0) ÷ 100 [1] = 28.109 = 28.1 [1]. Examiner insight: a correct final answer normally earns both marks even with no working, but a wrong answer with no working earns nothing; showing the products gives you a route to the method mark.

5. (a) Atomic number (proton number) [1]. (b) Elements are arranged in order of atomic number, not relative atomic mass [1]. Argon has atomic number 18 and potassium 19, so argon comes first (and this keeps each in a group with similar elements) [1]. (c) The same number of occupied electron shells [1]. Examiner insight: in (b) the second mark needs the comparison of atomic numbers; repeating the Ar values from the stem earns nothing.

6. (a) 2,7 [1] (b) 2,8,3 [1] (c) 2,8,8,1 [1] Examiner insight: configurations must be written in shell order from the nucleus outwards; 1,8,8,2 or 8,8,2,1 style reversals are not credited.

7. (a) Group 2 [1]; Period 3 [1]. (b) Magnesium [1]. (c) Beryllium or calcium [1]. Both have 2 electrons in the outer shell, and reactions involve the outer-shell electrons [1]. Examiner insight: in (c) “in the same group” alone usually earns no explanation mark, because it restates the question; the mark is for the same number of outer-shell electrons.

8. (a) W: metal; the oxide gives an alkaline solution, so it is a basic oxide [1]. X: non-metal; the oxide gives an acidic solution, so it is an acidic oxide [1]. Y: metal; the oxide reacts with an acid to form a salt and water, so it is basic [1]. Z: non-metal; the oxide gives an acidic solution (pH below 7) [1]. (b) Z is carbon (graphite), a non-metal that conducts electricity, so conductivity alone would suggest a metal [1]. (c) Add the oxide of Y to dilute acid (and warm) [1]. The oxide reacts and dissolves, neutralising the acid and forming a salt and water (the pH of the mixture rises) [1]. Examiner insight: each classification in (a) needs its reason; “metal” with no reference to the oxide or its pH scores nothing for that element.

9. (a) Both atoms have one electron in the outer shell [1]. Chemical reactions involve the outer-shell electrons, so they react in similar ways [1]. (b) Neon has a full outer shell (2,8) [1]. This is a stable arrangement, so it has no tendency to lose, gain or share electrons [1]. (c) Its outer shell (the first shell) is full with two electrons [1]. Examiner insight: “stable” on its own is not enough in (b); the second mark needs the idea that the atom does not need to lose, gain or share electrons.

10. (a) Let the percentage of chlorine-35 be x, so chlorine-37 is (100 − x). (35x + 37(100 − x)) ÷ 100 = 35.5 [1] 3700 − 2x = 3550 [1] x = 75% [1]. (b) 2,8,7 [1]. (c) Three occupied shells, so Period 3 [1]. Seven electrons in the outer shell, so Group 7 [1]. (d) Below 7 (acidic) [1]. Chlorine is on the right of the Periodic Table, so it is a non-metal, and non-metal oxides are acidic [1]. Examiner insight: in (a) setting up the weighted-mean equation earns the first mark even if the algebra later goes wrong; a guess of “75%” justified only by “35.5 is nearer 35” earns at most the final mark.

11. (a) Ar = (39 × 93.3 + 41 × 6.7) ÷ 100 = (3638.7 + 274.7) ÷ 100 [1] = 39.134 = 39.1 [1]. (b) 19 protons and 19 electrons [1]; 22 neutrons [1]. (c) 2,8,8,1 [1]; Group 1, Period 4 [1]. (d) Add potassium oxide to water containing universal indicator [1]. The indicator turns blue or purple: the solution is alkaline (pH above 7), so the oxide is basic, which shows a metal [1]. (e) Both have one electron in the outer shell [1], and chemical reactions involve the outer-shell electrons [1]. Examiner insight: in (a) the instruction “to 1 decimal place” is part of the accuracy mark, so 39.13 or 39 can lose it even when the working is correct; Ar also has no units.

Where marks are usually lost

• Writing the electron’s relative mass as 0 instead of a very small value such as 1/1840.
• Counting electrons in a positive ion as more than the protons.
• Using mass number instead of atomic number when counting electrons.
• Dividing by 100 when the abundances are a ratio, or forgetting to divide at all.
• Rounding Ar to a whole number when 1 decimal place is asked for.
• Writing 2,8,9 for potassium: the third shell holds 8 for the first 20 elements.
• Explaining similar properties with “same group” instead of “same number of outer-shell electrons”.
• Saying noble gases have “8 outer electrons” without allowing for helium’s full shell of 2.
• Classifying an element without using the oxide evidence the question gives.

Next steps

• Condensed recall: atomic structure and Periodic Table revision notes
• Full teaching: atomic structure and Periodic Table study guide
• Use Ar in mole calculations: chemical formulae, equations and calculations practice
• 4CH1 Chemistry course hub and printable 4CH1 checklist
• Find your weak spots: the free 4CH1 all-topics diagnostic
• Book a free trial class

Official syllabus

Pearson Edexcel International GCSE in Chemistry (4CH1) specification, Issue 3, September 2024, published by Pearson Education Limited. Topic 1 Principles of chemistry, sub-topics (c) Atomic structure (points 1.14–1.17) and (d) The Periodic Table (points 1.18–1.24).