Atomic Structure and Bonding Revision

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Part 1: Atomic structure and the periodic table

Instructions: Answer all 20 questions. Show your working where appropriate.

1. Subatomic particles (3 marks)

Complete the table.

Proton: relative charge ________ relative mass ________

Neutron: relative charge ________ relative mass ________

Electron: relative charge ________ relative mass ________

2. Atomic structure (2 marks)

State the location of protons, neutrons and electrons in an atom. Include the name of the central part of the atom.

3. Atomic number and mass number (3 marks)

An atom contains 17 protons, 18 neutrons and 17 electrons. State its atomic number and mass number. Explain how you know it is an atom rather than an ion.

4. Isotopes (2 marks)

Explain what is meant by the term isotopes.

5. Isotope calculation (3 marks)

Chlorine has two isotopes: chlorine-35 and chlorine-37. For each isotope, calculate the number of neutrons in one atom.

6. Electronic structure (3 marks)

Write the electronic structure of each atom:

a) Magnesium, atomic number 12: ____________________

b) Oxygen, atomic number 8: ____________________

c) Potassium, atomic number 19: ____________________

7. Forming ions (3 marks)

Explain how a magnesium atom forms a Mg²⁺ ion. Include the change in the number of electrons and the electronic structures of the atom and ion.

8. The periodic table (3 marks)

Choose the correct answer for each statement.

a) The atomic number of an element is the number of:

Neutrons

Protons

Electron shells

b) Elements in the same group have the same number of:

Protons

Outer-shell electrons

Neutrons

c) The number of occupied electron shells shows the element's:

Group

Period

Relative atomic mass

9. Group properties (3 marks)

Describe how the reactivity of Group 1 metals changes down the group. State how the reactivity of Group 7 elements changes down the group.

10. Predicting an element's properties (3 marks)

Element X has the electronic structure 2,8,1. Identify its group and period, state whether it is a metal or non-metal, and predict the charge of its ion.

Part 2: Bonding, structure and properties

11. Ionic bonding (3 marks)

Use a dot-and-cross diagram to show the formation of magnesium oxide, MgO. Show the electron transfer and the charges on both ions.

12. Ionic structures and properties (3 marks)

Explain why solid sodium chloride has a high melting point and does not conduct electricity, whereas molten sodium chloride does conduct electricity.

13. Covalent bonding (3 marks)

Draw a displayed formula for a molecule of water, H₂O. Show the covalent bonds and state what a covalent bond is.

14. Simple molecular substances (2 marks)

Explain why simple molecular substances usually have low melting and boiling points.

15. Giant covalent structures (3 marks)

Compare the structure and properties of diamond and graphite. Explain one reason why their properties are different.

16. Metallic bonding (3 marks)

Describe metallic bonding and explain why metals conduct electricity.

17. Alloys (2 marks)

Explain why an alloy is usually harder than a pure metal.

Part 3: Particle model and properties of matter

18. States of matter (3 marks)

Describe the arrangement and movement of particles in a gas. Use the particle model to explain why gases can be compressed.

19. Changes of state (3 marks)

Explain what happens to particles when a solid melts. State whether energy is absorbed or released and describe the change in the forces between particles.

20. Density calculation (3 marks)

A metal block has a mass of 270 g and a volume of 100 cm³. Calculate its density in g/cm³. Show your working and include the unit.

Answer key and mark scheme

1. Proton: charge +1, mass 1. Neutron: charge 0, mass 1. Electron: charge −1, very small/negligible mass. (3)

2. Protons and neutrons are in the nucleus; electrons are in shells around the nucleus. (2)

3. Atomic number = 17; mass number = 17 + 18 = 35. It is an atom because it has equal numbers of protons and electrons, so it has no overall charge. (3)

4. Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. (2)

5. Chlorine-35: 35 − 17 = 18 neutrons. Chlorine-37: 37 − 17 = 20 neutrons. (3)

6. a) 2,8,2. b) 2,6. c) 2,8,8,1. (3)

7. Magnesium loses two electrons to form Mg²⁺; Mg is 2,8,2 and Mg²⁺ is 2,8. (3)

8. a) Protons. b) Outer-shell electrons. c) Period. (3)

9. Group 1 reactivity increases down the group. Group 7 reactivity decreases down the group. (3)

10. Group 1; period 3; metal; forms a 1+ ion. (3)

11. Magnesium loses two outer-shell electrons and oxygen gains two electrons. The diagram shows Mg²⁺ and O²⁻, each with a full outer shell, with the transferred electrons clearly identified. (3)

12. Strong electrostatic attractions between oppositely charged ions require lots of energy to overcome, giving a high melting point. In solid sodium chloride the ions cannot move, but in the molten substance the ions can move and carry charge. (3)

13. The displayed formula is H–O–H, with two covalent bonds. A covalent bond is a shared pair of electrons between atoms. (3)

14. The forces between molecules are weak, so only a small amount of energy is needed to overcome them. (2)

15. Diamond has a giant structure in which each carbon forms four strong covalent bonds, making it hard and unable to conduct electricity. Graphite has layers in which each carbon forms three covalent bonds; weak forces between layers allow them to slide, and delocalised electrons allow it to conduct electricity. Any valid comparison with explanation. (3)

16. Metals consist of positive ions surrounded by delocalised electrons. The electrons are free to move and carry electrical charge through the metal. (3)

17. Different-sized atoms distort the regular layers in an alloy, making it more difficult for the layers to slide. (2)

18. Gas particles are far apart and move randomly in all directions. There are large gaps between them, so the particles can be pushed closer together. (3)

19. Particles gain energy and vibrate more until they leave their fixed positions and can move past one another. Energy is absorbed, and the forces holding the particles in fixed positions are overcome or weakened. (3)

20. Density = mass ÷ volume = 270 ÷ 100 = 2.7 g/cm³. (3)

Total: 57 marks