A Level H1 Chemistry Periodic Table Quiz

A-Level Chemistry H1 Quiz - Periodic Table (Answer Key)

1. C
[1]

2. C
[1]

3.

• The electron removed from Al is from a 3p orbital, whereas the electron removed from Mg is from a 3s orbital. [1]
• The 3p orbital is higher in energy and further from the nucleus (and experiences more shielding) than the 3s orbital, making it easier to remove. [1]
  [2]

4.

• Trend: Melting point increases from chlorine to iodine. [1]
• Explanation: The molecules become larger with more electrons. [1]
• This leads to stronger van der Waals’ forces (London dispersion forces) between molecules, requiring more energy to overcome. [1]
  [3]

5.
PCl₅(s) + 4H₂O(l) → H₃PO₄(aq) + 5HCl(aq)
[1] for correct formulae, [1] for balancing and state symbols.
[2]

6.
(a)

• Across the period, the number of protons (nuclear charge) increases. [1]
• Electrons are added to the same principal quantum shell, so shielding remains similar. The increased nuclear attraction pulls electrons closer, making them harder to remove. [1]
  [2]

(b)

• In sulfur, the electron is removed from a paired 3p orbital. [1]
• Electron-electron repulsion within the paired orbital makes it easier to remove the electron compared to phosphorus, where the 3p electron is unpaired. [1]
  [2]

7.
(a)

• Giant metallic structure. [1]
• Consists of Mg²⁺ cations in a sea of delocalised electrons, held by strong electrostatic forces. [1]
  [2]

(b)

• Sulfur consists of simple molecular structures (S₈) held together by weak van der Waals’ forces. [1]
• Magnesium has strong metallic bonding. Less energy is required to overcome the weak intermolecular forces in sulfur than the strong metallic bonds in magnesium. [1]
  [2]

8.
(a)
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
[1]

(b)

• Sodium floats / moves rapidly on the surface / melts into a sphere / effervescence. (Any one) [1]
  [1]

(c)

• Sodium has a larger atomic radius and lower nuclear charge compared to magnesium (within the same period context, but primarily group trend logic applies if comparing Na/Mg reactivity generally, but here it's period).
• Correction for Period 3 context: Sodium has only one valence electron to lose, while magnesium has two. The first ionisation energy of Na is much lower than Mg, making it easier for Na to lose its electron and react. [1]
• Also, Na⁺ has a lower charge density than Mg²⁺, resulting in weaker attraction for the remaining electrons, facilitating ionisation. [1]
  [2]

9.
(a)

• A reaction in which the same element is both oxidised and reduced. [1]
  [1]

(b)
Cl₂(g) + H₂O(l) ⇌ HCl(aq) + HClO(aq)
[1]

(c)

• In HCl: -1 [0.5]
• In HClO: +1 [0.5]
  [1]

10.
(a)

• An oxide that can react with both acids and bases to form a salt and water. [1]
  [1]

(b)
Al₂O₃(s) + 6HCl(aq) → 2AlCl₃(aq) + 3H₂O(l)
[1]

(c)
Al₂O₃(s) + 2NaOH(aq) + 3H₂O(l) → 2NaAl(OH)₄(aq)
(Or Na[Al(OH)₄])
[1]

11.
(a)

• Acidic (pH < 7). [1]
  [1]

(b)
SiCl₄(l) + 2H₂O(l) → SiO₂(s) + 4HCl(aq)
[1]

(c)

• Carbon has no available d-orbitals in its valence shell to expand its octet and accept lone pairs from water molecules. [1]
• Silicon has empty 3d orbitals that can accept lone pairs from water, allowing hydrolysis to occur. [1]
  [2]

12.
(a)

• Solubility decreases down the group. [1]
  [1]

(b)

• Thermal stability increases down the group. [1]
  [1]

(c)

• As the cation size increases down the group, the charge density decreases. [1]
• Lower charge density means less polarisation of the nitrate ion, making it harder to decompose (more stable). [1]
  [2]

13.
(a)

• N₂ consists of small non-polar molecules with weak van der Waals’ forces, so it is a gas. [1]
• P₄ consists of larger molecules with stronger van der Waals’ forces, so it is a solid. [1]
  [2]

(b)

• Nitrogen has a triple bond (N≡N) which is very strong and requires high energy to break. [1]
• Phosphorus has single bonds (P-P) which are weaker and more reactive. [1]
  [2]

14.
(a)

• Form coloured ions/compounds. [1]
• Have variable oxidation states. [1]
  (Other acceptable answers: act as catalysts, form complex ions)
  [2]

(b)

• Scandium only forms the Sc³⁺ ion. [1]
• Sc³⁺ has an empty d-subshell (3d⁰), so it does not exhibit typical transition element properties like coloured ions or variable oxidation states. [1]
  [2]

15.
(a)

• Potassium has an additional electron shell compared to sodium. [1]
• This increases the atomic radius and shielding, outweighing the increased nuclear charge. [1]
  [2]

(b)

• Potassium will have a lower first ionisation energy. [1]
• The outer electron is further from the nucleus and more shielded, so the attraction is weaker and less energy is required to remove it. [1]
  [2]

16.
(a)

• MgO has a giant ionic lattice structure with strong electrostatic forces between Mg²⁺ and O²⁻ ions. [1]
• P₄O₁₀ has a simple molecular structure with weak van der Waals’ forces between molecules. [1]
  [2]

(b)

• Al³⁺ has a high charge density, which polarises the oxide ion, giving the bond significant covalent character. This allows it to react with bases. [1]
• Mg²⁺ has a lower charge density, so MgO is predominantly ionic and basic. [1]
  [2]

17.
(a)
M(s) + 2H₂O(l) → M(OH)₂(aq) + H₂(g)
[1]

(b)

• Down the group, the lattice energy of the hydroxide decreases more rapidly than the hydration energy. [1]
• This makes the hydroxides more soluble, releasing more OH⁻ ions into solution, resulting in a higher pH. [1]
  [2]

18.
(a)
Cl₂ + 2OH⁻ → Cl⁻ + ClO⁻ + H₂O
[1]

(b)

• Sodium chlorate(I) (or bleach/disinfectant). [1]
  [1]

19.
(a)

• Red-brown liquid. [1]
  [1]

(b)

• Observation: Solution turns orange/brown. [1]
• Equation: Cl₂ + 2Br⁻ → 2Cl⁻ + Br₂ [1]
  [2]

20.
(a)

• The power of an atom to attract the bonding pair of electrons in a covalent bond. [2]
  [2]

(b)

• Nuclear charge increases across the period. [1]
• Shielding remains constant (same shell), so the attraction for bonding electrons increases. [1]
  [2]