Chemical periodicity of other elements
Cambridge A-Level Chemistry (9701) · Unit 9: The Periodic Table: chemical periodicity · 8 flashcards
Chemical periodicity of other elements is topic 9.3 in the Cambridge A-Level Chemistry (9701) syllabus , positioned in Unit 9 — The Periodic Table: chemical periodicity .
Marked as AS Level: examined at AS Level in Paper 1 (Multiple Choice), Paper 2 (AS Structured Questions) and Paper 3 (Advanced Practical Skills). The same content may also be assumed in Paper 4 (A Level Structured Questions).
The deck below contains 8 flashcards — 2 definitions, 4 key concepts and 2 calculations — covering the precise wording mark schemes reward. Use the 2 definition cards to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
Some cards in this deck are on other syllabus topics: 10.1 Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds and 11.1 Physical properties of the Group 17 elements. Each card is labelled with its topic.
What the Cambridge 9701 syllabus says
2025-2027 syllabus, in our words · AS LevelWhat the syllabus expects you to be able to do in this topic, in plain English. For the exact wording, see the official syllabus (PDF).
- Use your knowledge of periodic trends to predict the typical properties of an element when you know which group it is in.
- Use given data on the physical and chemical properties of an unknown element to work out what kind of element it is, where it could sit in the Periodic Table and which element it is.
Also in this deck: 10.1 Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
- For the Group 2 metals, magnesium to barium, describe how each reacts with oxygen, with water and with dilute HCl and dilute H₂SO₄, and write equations for these reactions.
- Describe how the Group 2 oxides, hydroxides and carbonates react with water, dilute HCl and dilute H₂SO₄, giving an equation for each reaction.
- Describe, with equations, how Group 2 nitrates and carbonates break down when heated, including how their thermal stability changes down the group.
- Describe the trends down Group 2 in the physical and chemical properties of the metals (in their reactions with oxygen, water and dilute acids) and of their oxides, hydroxides, carbonates, nitrates and sulfates, and use these trends to make predictions.
- State how the solubility of the Group 2 hydroxides, and of the Group 2 sulfates, changes down the group.
Also in this deck: 11.1 Physical properties of the Group 17 elements
- Describe the colour of chlorine, of bromine and of iodine, and how volatile they are relative to one another.
- Describe how the bond strength in halogen molecules changes down the group, and explain why.
- Explain why the halogens differ in volatility in terms of the forces between their molecules: instantaneous dipole-induced dipole attractions.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9701 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Tips to avoid common mistakes in these topics
- › Memorize the balanced equation for the decomposition of Group 2 nitrates: 2M(NO3)2 → 2MO + 4NO2 + O2.
- › Recall that MgO is basic and reacts with acids; differentiate between soluble Ba(OH)2 and insoluble BaSO4 during residue analysis.
- › Remember that thermal stability increases down Group 2 and that NO2 is an acidic gas that turns moist indicator paper red.
- › Define a volatile substance as one that evaporates easily or has a high vapor pressure at room temperature.
- › Recall halogen states at 293 K: chlorine is a pale green gas, bromine is a red-brown liquid, and iodine is a grey-black solid.
Topic 10.1 · Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
How does the reactivity of Group 2 metals with water change down the group, and why?
Reactivity with water increases down Group 2. Down the group the outer electrons are further from the nucleus and more shielded, so the first and second ionisation energies decrease and the two outer electrons are lost more easily. Magnesium reacts only very slowly with cold water (but readily with steam), while calcium, strontium and barium react with cold water increasingly vigorously, forming the hydroxide and hydrogen.
Topic 10.1 · Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
Describe the trend in thermal stability of Group 2 carbonates.
Thermal stability increases down Group 2 carbonates (MgCO₃ < CaCO₃ < SrCO₃ < BaCO₃). This is because the larger the cation (
Topic 10.1 · Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
Write a balanced equation for the reaction of strontium with oxygen.
2Sr(s) + O₂(g) → 2SrO(s)
Topic 10.1 · Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
State the trend in solubility of Group 2 hydroxides in water.
The solubility of Group 2 hydroxides increases down the group. Mg(OH)₂ is sparingly soluble, while Ba(OH)₂ is significantly more soluble.
Topic 11.1 · Physical properties of the Group 17 elements
Describe the trend in volatility of the halogens (Cl₂, Br₂, I₂).
Volatility decreases down the halogens (Cl₂ > Br₂ > I₂). This is because the strength of instantaneous dipole-induced dipole forces (van der Waals forces) increases with increasing number of electrons and molecular size.
Topic 11.1 · Physical properties of the Group 17 elements
Explain the trend in bond strength of halogen molecules (Cl₂, Br₂, I₂).
Bond strength decreases down the halogens (Cl₂ > Br₂ > I₂). This is due to increased bond length and decreased orbital overlap as the atomic size of the halogen increases.
Topic 11.1 · Physical properties of the Group 17 elements
What are the colours of chlorine, bromine, and iodine at room temperature and pressure?
Chlorine (Cl₂) is a pale green gas. Bromine (Br₂) is a reddish-brown liquid. Iodine (I₂) is a dark grey/purple solid.
Topic 10.1 · Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
Write a balanced equation for the thermal decomposition of magnesium nitrate.
2Mg(NO₃)₂(s) → 2MgO(s) + 4NO₂(g) + O₂(g)
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