Lesson 3.2.1.2

3.2.1.2 Physical properties of Period 3 elements Quiz: AQA Chemistry, Unit 2

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

In partnership with Revision Ninja

Lesson 3.2.1.2, Physical properties of Period 3 elements: 20 multiple choice questions for the AQA Chemistry (7405), Unit 2: Inorganic chemistry, written with Revision Ninja.

Host it live on the board and students join with a game code on their own devices, or revise alone with Free Play. The answers are revealed in the game.

Host this setFree Play

The 20 questions

  1. How does atomic radius change across Period 3 from sodium to chlorine?

    • It stays the same, because all Period 3 elements have the same number of shells
    • It decreases, because nuclear charge increases while the electrons stay in the same shell
    • It increases then decreases, because the shielding changes sharply at silicon
    • It increases, because each added electron moves into a new, larger shell

  2. Why does atomic radius decrease across Period 3?

    • The number of shells increases, so the atoms become smaller in size as more protons are added to them
    • The electrons are removed from the atoms, so the atoms shrink as the period goes on and more charge builds up
    • The number of neutrons increases, so the nucleus repels the outer electrons more strongly across the period
    • Nuclear charge increases while shielding stays similar, so the outer electrons are pulled closer to the nucleus

  3. Which Period 3 element has the largest atomic radius?

    • Sodium
    • Aluminium
    • Chlorine
    • Magnesium

  4. What is the general trend in first ionisation energy across Period 3 from Na to Ar?

    • It increases steadily with no exceptions from sodium to argon
    • It generally increases, with dips at aluminium and sulfur
    • It is the same for all Period 3 elements
    • It decreases steadily from sodium to argon

  5. Why is the first ionisation energy of magnesium higher than that of sodium?

    • Sodium has more shielding from neutrons, so its outer electron is removed more easily
    • Sodium has a higher nuclear charge, so its outer electron is held more strongly than in magnesium
    • Magnesium has a greater nuclear charge and its outer electrons are in the same shell, so they are held more strongly
    • Magnesium has an extra shell, so its outer electrons are further from the nucleus

  6. The first ionisation energy falls from magnesium to aluminium. Which explanation is correct?

    • Aluminium has fewer protons than magnesium, so its outer electron is held more weakly by the nucleus overall
    • Aluminium has more shielding from neutrons, which reduces its outer electron attraction to the nucleus strongly
    • Aluminium has an extra shell, so its outer electron is much further from the nucleus than the magnesium electron
    • The outer electron of aluminium is in a 3p subshell, which is higher in energy than 3s and slightly further from the nucleus

  7. The first ionisation energy falls from phosphorus to sulfur. Which explanation is correct?

    • Sulfur has a paired electron in one 3p orbital, and the repulsion between the paired electrons makes one easier to remove
    • Sulfur has no outer electrons in a 3p subshell, so its first ionisation energy is lower than that of phosphorus
    • Sulfur has an extra shell, so its outer electrons are further from the nucleus and are held less tightly overall
    • Sulfur has fewer protons than phosphorus, so its outer electrons are held more weakly by the nucleus overall

  8. Which element in Period 3 has the highest melting point, and why?

    • Argon, because it has the largest atomic radius in the period, so its atoms are held together more strongly
    • Sodium, because it has the most delocalised electrons per atom in the period
    • Silicon, because it has a giant covalent structure with many strong covalent bonds
    • Phosphorus, because it has the most strong intermolecular forces between its molecules in the solid form

  9. Why does magnesium have a higher melting point than sodium?

    • Magnesium has a larger atomic radius, so its metallic bonds are longer and weaker and it melts at a lower point
    • Magnesium forms covalent molecules, which need more energy to melt than metallic bonds, so it melts at a higher point
    • Magnesium has fewer delocalised electrons than sodium, so its metallic bonding is weaker and it melts more easily
    • Magnesium has two delocalised electrons per atom and a higher positive charge on its ions, so its metallic bonding is stronger

  10. Why do phosphorus, sulfur, chlorine and argon have low melting points compared with silicon?

    • They are ionic compounds with low lattice enthalpies, so the ions separate easily when the solid is heated gently
    • They have giant covalent structures in which the bonds are very weak, so they melt at low temperatures in every case
    • They are simple molecular or atomic substances held together by weak London forces between molecules or atoms
    • They are metals with few delocalised electrons, so their metallic bonds are weak and they melt easily at room temperature

  11. Which Period 3 element has the lowest melting point?

    • Argon, which is monatomic with only weak London forces between atoms
    • Silicon, which has the simplest structure of all the elements in the period
    • Sodium, which has the fewest delocalised electrons per atom in the period
    • Chlorine, which has the smallest molecules in the period, held together by weak forces

  12. Why is the first ionisation energy of argon higher than that of chlorine?

    • Argon has no electrons in its outer shell, so it cannot lose an electron at all
    • Argon has an extra shell that gives more shielding, so its outer electron is harder to remove
    • Argon has one more proton, and its outer electron is in a full 3p subshell that is held more strongly
    • Argon has fewer protons, so its outer electron is held more strongly than in chlorine

  13. Why is the first ionisation energy of silicon higher than that of aluminium?

    • Silicon has more shielding from neutrons, which reduces the attraction on its outer electron
    • Silicon has one more proton, and its outer electron is in the same 3p subshell with a greater nuclear attraction
    • Silicon has an extra shell, so its outer electron is further from the nucleus
    • Silicon has fewer electrons in its outer shell, so it holds them more tightly

  14. Which factor does NOT explain the trend in atomic radius across Period 3?

    • The attraction of the outer electrons by the nucleus, which becomes stronger as more protons are added
    • Similar shielding of the outer electrons by the inner shells, which stays roughly constant across the period
    • A change in the number of electron shells, since all Period 3 atoms have three shells
    • An increase in nuclear charge across the period, which pulls the outer electrons in more strongly each time

  15. Explain why the atomic radius of sodium is larger than that of chlorine.

    • Sodium has more neutrons, which push the outer electrons away from the nucleus
    • Sodium has more electron shells, so its outer electrons are further from the nucleus
    • Sodium has fewer protons, so its nucleus pulls the outer electrons less strongly than chlorine does
    • Chlorine has fewer electrons, so its atom is physically smaller in size

  16. Describe the general trend in melting point across Period 3 from sodium to silicon.

    • It rises from sodium to silicon, then falls steadily to argon without any exceptions
    • It rises from sodium to silicon, where the giant covalent structure gives the maximum
    • It falls steadily from sodium to silicon, because silicon is a gas at room temperature
    • It is the same for all four elements, because they all have metallic bonding

  17. Why is the first ionisation energy of sodium lower than that of magnesium?

    • Sodium has a higher nuclear charge, so its outer electron is held less strongly than in magnesium
    • Sodium has more shells than magnesium, so its outer electron is closer to the nucleus
    • Sodium has a single electron in its outer 3s subshell that is held less strongly than the two in magnesium
    • Sodium has more paired electrons in its outer subshell, which makes it easier to lose one

  18. Which statement about the melting points of phosphorus, sulfur and chlorine is correct?

    • They are low because they are molecular substances with weak forces between the molecules
    • They are high because they are metals with many delocalised electrons
    • They are high because they are giant covalent solids with strong bonds throughout
    • They are low because they are ionic solids with weak electrostatic forces

  19. The first ionisation energy of Na is 496 kJ/mol and of Mg is 738 kJ/mol. What is the difference between them?

    • 738 kJ/mol
    • 1234 kJ/mol
    • 496 kJ/mol
    • 242 kJ/mol

  20. What is the first ionisation energy of sodium, in kJ/mol?

    • 578 kJ/mol
    • 496 kJ/mol
    • 1251 kJ/mol
    • 738 kJ/mol

All AQA Chemistry quizzes