Practice questions: Matter and the Atomic Structure

Attempt every question before reading the answer. The multiple-choice section is written in the style of Paper 1 is an objective (multiple-choice) paper; the structured section is in the style of Paper 2 Section A. All questions are original, not reproduced from past-year papers.

Section A, Multiple-choice (Paper 1 style)

1. Which describes the arrangement of particles in a gas?

• A. Closely packed in an orderly pattern
• B. Far apart in a random arrangement
• C. Close together but not orderly
• D. Fixed in position, vibrating

Answer: B. In a gas the particles are far apart and randomly arranged with negligible forces between them.

2. According to the kinetic theory, when a substance is heated its particles:

• A. move more slowly
• B. increase in size
• C. gain kinetic energy and move faster
• D. stop moving

Answer: C. Heating increases the kinetic energy of the particles, so they move faster; the particles themselves do not change size.

3. In which state does diffusion occur most quickly?

• A. Solid
• B. Liquid
• C. Gas
• D. The same in all three

Answer: C. Gas particles are far apart and move fastest, so diffusion is quickest in gases.

4. During melting, the temperature stays constant on a heating curve because the heat supplied is used to:

• A. raise the kinetic energy of the particles
• B. overcome the forces of attraction between the particles
• C. increase the size of the particles
• D. create new particles

Answer: B. The heat weakens the forces holding the lattice together, not the kinetic energy, so the temperature holds steady.

5. The change of a solid directly into a gas is called:

• A. melting
• B. condensation
• C. sublimation
• D. freezing

Answer: C. Sublimation is the direct solid-to-gas change, with no liquid stage.

6. Which scientist proposed that an atom has a small, dense, positively charged nucleus?

• A. John Dalton
• B. J. J. Thomson
• C. Ernest Rutherford
• D. James Chadwick

Answer: C. Rutherford’s nuclear model placed a small dense positive nucleus at the centre of the atom.

7. Which subatomic particle has a relative mass that is effectively negligible?

• A. Proton
• B. Neutron
• C. Electron
• D. Nucleus

Answer: C. The electron has a relative mass of about 1/1840, negligible compared with the proton and neutron.

8. An atom has proton number 12 and nucleon number 25. How many neutrons does it contain?

• A. 12
• B. 13
• C. 25
• D. 37

Answer: B. Neutrons = nucleon number − proton number = 25 − 12 = 13.

9. Two atoms are isotopes of the same element if they have:

• A. the same nucleon number
• B. the same number of neutrons
• C. the same proton number but different nucleon numbers
• D. the same number of electrons after forming ions

Answer: C. Isotopes share the proton number (same element) but differ in nucleon number (different neutrons).

10. An atom has the electron arrangement 2.8.6. Its position in the periodic table is:

• A. Group 6, Period 2
• B. Group 16, Period 3
• C. Group 8, Period 3
• D. Group 6, Period 8

Answer: B. Six valence electrons place it in Group 16; three occupied shells place it in Period 3.

Section B, Structured questions (Paper 2 style)

Structured Question 1. A solid substance is heated steadily from room temperature. Its temperature rises, then stays constant at its melting point, then rises again.

• (a) Name the process taking place while the temperature is constant.
• (b) Explain, in terms of particles, why the temperature stays constant during this time.
• (c) Describe how the arrangement and movement of the particles change as the solid becomes a liquid.

Model answer. (a) Melting. (b) The heat energy supplied is used to overcome the forces of attraction holding the particles in the fixed solid lattice, rather than to increase their kinetic energy; because the average kinetic energy does not change, the temperature stays constant until melting is complete. (c) In the solid the particles are closely packed in an orderly arrangement and only vibrate about fixed positions; as it becomes a liquid the particles are still close together but no longer orderly, and they can now slide past one another and move about.

Structured Question 2. Atom X has a proton number of 19 and a nucleon number of 39.

• (a) State the number of protons, neutrons and electrons in a neutral atom of X.
• (b) Write the electron arrangement of X.
• (c) State the group and period of X in the periodic table.
• (d) Define the term isotope.

Model answer. (a) Protons = 19; electrons = 19 (equal to protons in a neutral atom); neutrons = 39 − 19 = 20. (b) 2.8.8.1. (c) Group 1 (one valence electron) and Period 4 (four occupied shells). (d) Isotopes are atoms of the same element that have the same proton number but different nucleon numbers (that is, different numbers of neutrons).

Structured Question 3. The model of the atom developed over time.

• (a) State one contribution each of Dalton, Thomson and Chadwick to the model of the atom.
• (b) An atom has 13 electrons. Write its electron arrangement and state the number of valence electrons.
• (c) Explain why this atom is electrically neutral.

Model answer. (a) Dalton, the atom is a tiny, indivisible sphere; Thomson, discovered the electron and proposed the plum-pudding model; Chadwick, discovered the neutron in the nucleus. (b) 2.8.3; there are 3 valence electrons. (c) The atom has 13 protons (each +1) and 13 electrons (each −1); the equal numbers of positive and negative charges cancel exactly, so the atom carries no overall charge.

How to use this set

Mark yourself strictly: for the structured questions, award a point only where your wording matches the reason given, especially the phrases “overcome the forces of attraction” and “same proton number, different nucleon number”. A one-to-one teacher can check the parts you got wrong and show you the exact phrasing the marking scheme expects. Then revisit the revision notes for any standard you missed.