Home / H2 Chemistry 9476 / Structured Practice: The Periodic Table (A Level) Exit to H2 Chemistry 9476 Structured Practice: The Periodic Table (A Level) Short, exam-style questions to practise trend explanations, Group 2/17 logic, and unknown-element deduction.
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Periodic trend anomaly: Mg to Al ionisation energy.
Part a: Which element has the lower first ionisation energy, Mg or Al? (1 mark) Use the correct element-symbol case and ionic charge. A substance name is accepted where appropriate. Part b: State one reason for this anomaly. (1 mark) Period 3 oxides and chlorides language.
Consider $\ce{Na2O}$, $\ce{MgO}$, $\ce{Al2O3}$ and $\ce{SiO2}$.
Part a: Identify the amphoteric oxide. (1 mark) Use the correct element-symbol case and ionic charge. A substance name is accepted where appropriate. Part b: State the overall acid-base trend in Period 3 oxides from Na to Si. (1 mark) Part c: Write equations showing that $\ce{Al(OH)3}$ is amphoteric. (2 marks) Group 2 reducing strength and carbonate stability.
Given $E^\ominus(\ce{Mg^{2+}/Mg})=-2.37\ \mathrm{V}$ and $E^\ominus(\ce{Ba^{2+}/Ba})=-2.90\ \mathrm{V}$.
Part a: Identify the stronger reducing agent. (1 mark) Use the correct element-symbol case and ionic charge. A substance name is accepted where appropriate. Part b: Explain your choice using the signs and meanings of the supplied values. (2 marks) Part c: Explain why $\ce{BaCO3}$ is more thermally stable than $\ce{MgCO3}$. (2 marks) Group 17 electrode potentials and hydrogen-halide stability.
Given $E^\ominus(\ce{Cl2/Cl^-})=+1.36\ \mathrm{V}$ and $E^\ominus(\ce{Br2/Br^-})=+1.07\ \mathrm{V}$.
Part a: Identify the stronger oxidising agent. (1 mark) Use the correct element-symbol case and ionic charge. A substance name is accepted where appropriate. Part b: Write the ionic equation for the reaction of chlorine with bromide ions. (2 marks) Part c: Explain why $\ce{HCl}$ is more thermally stable than $\ce{HBr}$. (2 marks) An unknown Period 3 element is one of sodium, magnesium, aluminium or silicon. Use all three records to identify it, cross-check the conclusion and reject a plausible alternative. The rounded numerical data and observation record are authored teaching data, not learner measurements.
Successive ionisation energies of the unknown Electron removed Energy / kJ mol⁻¹ 1 580 2 1820 3 2740 4 11600
Physical and chemical observations Test Observation Element at 20 °C Solid Melting point 660 ± 20 °C Electrical conduction Conducts readily as a solid and when molten Oxide with dilute hydrochloric acid Solid dissolves Oxide with warm concentrated aqueous sodium hydroxide Solid dissolves Chloride with excess water Acidic solution; no white solid remains
Candidate comparison data for this task Candidate Approximate melting point / °C Chloride with excess water Sodium 98 Dissolves, approximately neutral solution Magnesium 650 Dissolves, slightly acidic solution Aluminium 660 Acidic solution; no white solid remains Silicon 1410 Acidic solution and a white solid
After which electron removal does the significant shell-boundary increase occur? Enter its number. Calculate the ratio of the energy immediately after that boundary to the energy immediately before it. Give two decimal places. Deduce the main-group number using modern numbering. What behaviour do the two oxide tests together establish? Which particle model accounts for ready electrical conduction in the solid element? Identify the element consistent with the complete evidence. Enter its symbol or name. A classmate suggests silicon because its chloride also gives an acidic solution. Which observation contradicts that suggestion? A learner first says 'the melting-point interval includes magnesium, so the unknown must be magnesium', then ignores the other records. What is wrong with that first inference? Now discard the ionisation, oxide and chloride records. Do room-temperature state, conduction and the melting-point interval alone uniquely distinguish magnesium from aluminium? Period 3 melting-point and conductivity patterns.
Consider $\ce{Na}$, $\ce{Mg}$, $\ce{Al}$, $\ce{Si}$, $\ce{P4}$, and $\ce{S8}$.
Part a: State the Period 3 substance with the highest melting point from this list. (1 mark) Use the correct element-symbol case and ionic charge. A substance name is accepted where appropriate. Part b: Explain why electrical conductivity is high for Al but low for Si at room temperature. (2 marks) Comparing the radii of four ions.
Consider the ions $\ce{S^{2-}}$, $\ce{Cl^-}$, $\ce{K+}$ and $\ce{Ca^{2+}}$. Proton numbers: S 16, Cl 17, K 19, Ca 20.
Part a: State the number of electrons in each of these ions. (1 mark) Part b: Which list puts the ions in order of increasing ionic radius? (1 mark) Part c: Which statement explains the order? (1 mark) Part d: A potassium atom is larger than a chlorine atom. Explain why $\ce{K+}$ is nevertheless smaller than $\ce{Cl^-}$. (2 marks) Electrical conductivity from sodium to silicon.
The table gives approximate electrical conductivities of four Period 3 elements as solids at 298 K.
Electrical conductivity of four Period 3 elements at 298 K Element Outer-shell electrons per atom Electrical conductivity / S m⁻¹ Na 1 2.1 × 10⁷ Mg 2 2.3 × 10⁷ Al 3 3.8 × 10⁷ Si (pure) 4 about 4 × 10⁻⁴
Part a: Which statement best explains the trend from Na to Al? (1 mark) Part b: Silicon has more outer-shell electrons than aluminium. Which statement explains why it conducts far less well? (1 mark) Part c: A student claims that the more outer-shell electrons an element has, the better it conducts electricity. Use the data to evaluate this claim. (2 marks) Acid–base behaviour across Period 3.
Compare three Period 3 oxides: $\ce{Na2O}$, $\ce{Al2O3}$ and $\ce{P4O10}$.
Part a: Which describes the structure and bonding of the three oxides? (1 mark) Part b: Write a balanced equation for the reaction of $\ce{Na2O}$ with water, without state symbols. (1 mark) Part c: Write a balanced ionic equation for the reaction of $\ce{Al2O3}$ with $\ce{H+}$ ions in excess dilute acid, without state symbols. (1 mark) Part d: $\ce{Al2O3}$ also dissolves in excess aqueous sodium hydroxide, forming the tetrahydroxoaluminate ion, $\ce{[Al(OH)4]^-}$. Write a balanced equation for this reaction, without state symbols. (1 mark) Part e: Write a balanced equation for the reaction of $\ce{P4O10}$ with water, without state symbols. (1 mark) Part f: Explain, in terms of bonding and electronegativity, why the oxides change from basic through amphoteric to acidic across the period. (2 marks) Thermal decomposition of the Group 2 carbonates.
The table gives the radius of each Group 2 cation and the approximate temperature at which its carbonate decomposes.
Group 2 cation radii and carbonate decomposition temperatures Carbonate Cation radius / nm Approximate decomposition temperature / °C MgCO₃ 0.065 540 CaCO₃ 0.099 900 SrCO₃ 0.113 1280 BaCO₃ 0.135 1360
Part a: Write a balanced equation for the thermal decomposition of magnesium carbonate, without state symbols. (1 mark) Part b: When a Group 2 cation polarises the carbonate ion, which bond is weakened? (1 mark) Part c: Use the data to explain why magnesium carbonate decomposes at a lower temperature than barium carbonate. (3 marks) Part d: A student argues that barium carbonate is more thermally stable because barium is a more reactive metal than magnesium. Which evaluation is correct? (1 mark) Chlorine as an oxidising agent.
$\ce{Cl2 + 2e^- <=> 2Cl^-}$ $\quad E^\ominus=+1.36\ \text{V}$
$\ce{Br2 + 2e^- <=> 2Br^-}$ $\quad E^\ominus=+1.07\ \text{V}$
$\ce{I2 + 2e^- <=> 2I^-}$ $\quad E^\ominus=+0.54\ \text{V}$
When chlorine is bubbled into cold, dilute aqueous sodium hydroxide, the products are sodium chloride, $\ce{NaClO}$ and water.
Part a: Which halide ions does aqueous chlorine oxidise under standard conditions? (1 mark) Part b: State the oxidation number of chlorine in $\ce{ClO^-}$. (1 mark) Part c: State the oxidation number of chlorine in $\ce{Cl^-}$. (1 mark) Part d: Write the balanced ionic equation for the reaction of chlorine with cold, dilute hydroxide ions, without state symbols. (1 mark) Part e: Why is this reaction described as disproportionation? (1 mark) Identifying an element from its oxide and chloride.
An unknown Period 3 element X forms an oxide that reacts with both dilute hydrochloric acid and aqueous sodium hydroxide. The anhydrous chloride of X sublimes at about 180 °C, fumes in moist air and exists as dimers in the vapour.
Part a: Identify element X. (1 mark) Part b: Give the molecular formula of the chloride in the vapour. (1 mark) Part c: Which clue, on its own, does not rule out silicon as element X? (1 mark) Part d: The fumes form when the chloride reacts with water vapour. Write a balanced equation for this reaction, using the monomer formula of the chloride and without state symbols. (1 mark) Part e: Explain how the oxide clue and the chloride clues independently support your identification. (2 marks)