A Level H1 Chemistry Periodic Table Quiz

Answer Key - A-Level Chemistry H1 Quiz: Periodic Table

1. Trend: Decreases. [1] Explanation: Nuclear charge increases (more protons) [1] while shielding remains constant (electrons added to the same shell), resulting in a stronger attraction between the nucleus and valence electrons. [1]

2. Comparison: Magnesium has a higher first ionisation energy than aluminium. [1] Explanation: Mg has electrons in the $3s$ orbital, while Al has its outermost electron in the $3p$ orbital. [1] The $3p$ electron is further from the nucleus and more shielded by the $3s$ electrons, making it easier to remove. [1]

3. Prediction: Electronegativity increases. [1]

4. Explanation: Silicon has a higher nuclear charge than aluminium [1] and the valence electrons are in the same shell, leading to a stronger attraction for the bonding pair. [1]

5. Trend: Increases from Na to Si. [2] (Accept: Na < Mg < Al < Si)

6. Explanation: Silicon has a giant covalent structure [1] with strong covalent bonds throughout the lattice. [1] Phosphorus exists as simple molecular $\text{P}_4$ molecules [1] held by weak London dispersion forces.

7. Comparison: Sulfur has a higher boiling point than chlorine. [1] Justification: Both are simple molecular. Sulfur ($\text{S}_8$) has a larger molecular size/greater number of electrons than chlorine ($\text{Cl}_2$). [1] This leads to stronger London dispersion forces. [1]

8. Element: Sodium (Na). [1] Equation: $\text{Na}_2\text{O}(\text{s}) + \text{H}_2\text{O}(\text{l}) \to 2\text{NaOH}(\text{aq})$ [1]

9. (a) Nature: Amphoteric. [1] (b) Equation: $\text{Al}_2\text{O}_3(\text{s}) + 2\text{NaOH}(\text{aq}) + 3\text{H}_2\text{O}(\text{l}) \to 2\text{Na}[\text{Al}(\text{OH})_4](\text{aq})$ [2]

10. Comparison: Both are acidic. [2] (Accept: $\text{SiO}_2$ is weakly acidic/insoluble, $\text{P}_4\text{O}_{10}$ is strongly acidic).

11. Equation: $\text{SiO}_2(\text{s}) + 2\text{NaOH}(\text{aq}) \to \text{Na}_2\text{SiO}_3(\text{aq}) + \text{H}_2\text{O}(\text{l})$ [2]

12. Structure: Simple molecular. [1] Bonding: Covalent bonding. [1]

13. Comparison: $\text{Na}_2\text{O}$ is highly soluble [1]; $\text{Al}_2\text{O}_3$ is insoluble. [1]

14. Explanation: Sulfur in $\text{SO}_3$ is in the $+6$ oxidation state, while in $\text{SO}_2$ it is $+4$. [1] $\text{SO}_3$ is more electron-deficient and thus more strongly attracts electrons/is more easily reduced. [1]

15. Formula: $\text{MgCl}_2$ [1] Structure: Giant ionic lattice. [1]

16. Comparison: $\text{MgCl}_2$ has a higher boiling point than $\text{AlCl}_3$. [1] Explanation: $\text{MgCl}_2$ is a giant ionic structure with strong electrostatic attractions. [1] $\text{AlCl}_3$ is a simple molecular structure (dimer $\text{Al}_2\text{Cl}_6$) with weak intermolecular forces. [1]

17. Observation: White solid sublimes/decomposes into a white fume of $\text{PCl}_3$ and chlorine gas (pale green). [2]

18. Equation: $\text{AlCl}_3(\text{s}) + 6\text{H}_2\text{O}(\text{l}) \to [\text{Al}(\text{H}_2\text{O})_6]^{3+}(\text{aq}) + 3\text{Cl}^-(\text{aq})$ [2] pH: Acidic (pH < 7). [1]

19. Explanation: $\text{Si}$ is larger than $\text{P}$ (though both are Period 3, the steric accessibility differs) but more importantly, $\text{SiCl}_4$ has a more pronounced $\delta+$ on the central atom due to the electronegativity difference and the availability of empty $d$-orbitals for the nucleophilic attack of water. [3] (Accept: mention of empty $d$-orbitals and polarity).

20. Formula: $\text{SF}_6$ (Note: Question asks for chloride, but sulfur's highest oxidation state chloride $\text{SCl}_6$ is unstable; however, following syllabus trends for Period 3 halides, $\text{SF}_6$ is the standard example. If student writes $\text{SCl}_6$, accept based on oxidation state logic). [1] Shape: Octahedral. [1]