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Cambridge International AS Level Chemistry

Topic 9
The Periodic Table: Chemical Periodicity

Topic 9 covers the periodicity of physical properties across Period 3 (atomic and ionic radius, melting point, electrical conductivity), the reactions of the Period 3 elements and their oxides and chlorides, and using periodicity to predict the properties of unknown elements. These pages cover the physical periodicity of 9.1; the oxides and chlorides (9.2) and predictions (9.3) follow with a later set.

Exam Papers
Papers 1 & 2
9701/1 and 9701/2 (AS Level)
Learning Outcomes
9.1.1 – 9.3.2
3 parts
Topic Parts
1 of 3 live
9.1 Physical periodicity
Exam Board
Cambridge
CIE 9701 (2025-2027)

Revision Notes

Work through each part of Cambridge Topic 9 in a structured sequence.

Period 3
Periodic
Trends
1

9.1 Periodic Trends

Atomic radius, ionisation energy, melting point and conductivity across Period 3 explained by structure and bonding (9.1.1, 9.1.2).

Start revising
Radii
Atomic and
Ionic Radii
2

Atomic and Ionic Radii (Topic 1)

The periodicity of atomic and ionic radius across Radii, including the isoelectronic ions (9.1.1-a, 9.1.1-b), on the Topic 1 pages.

Start revising
Evidence
Ionisation
Energy
3

Ionisation Energy (Topic 1)

The ionisation energy trends across Period 3 and down a group, on the Topic 1 pages (1.4.3).

Start revising
Reactions
Oxides and
Chlorides
4
Coming soon

9.2 Period 3 Oxides and Chlorides

Reactions of the elements with oxygen, chlorine and water, and the acid-base behaviour of the oxides and chlorides. Coming with a later set.

In preparation
Predict
Using
Periodicity
5
Coming soon

9.3 Predicting Properties

Deducing the nature and position of unknown elements from their properties. Coming with a later set.

In preparation
Specification Coverage

Topic 9 The Periodic Table: Chemical Periodicity – Cambridge International AS Level Chemistry

The following Cambridge learning outcomes state what candidates should be able to do for Topic 9. Wording is taken from the Cambridge International AS & A Level Chemistry 9701 syllabus (2025-2027).

9.1 Periodicity of physical properties of the elements in Period 3

9.1.1
describe qualitatively (and indicate the periodicity in) the variations in atomic radius, ionic radius, melting point and electrical conductivity of the elements
9.1.2
explain the variation in melting point and electrical conductivity in terms of the structure and bonding of the elements

9.2 Periodicity of chemical properties of the elements in Period 3

9.2.1
describe, and write equations for, the reactions of the elements with oxygen (to give Na2O, MgO, Al2O3, P4O10, SO2), chlorine (to give NaCl, MgCl2, AlCl3, SiCl4, PCl5) and water (Na and Mg only)
9.2.2
state and explain the variation in the oxidation number of the oxides (Na2O, MgO, Al2O3, P4O10, SO2 and SO3 only) and chlorides (NaCl, MgCl2, AlCl3, SiCl4, PCl5 only) in terms of their outer shell (valence shell) electrons
9.2.3
describe, and write equations for, the reactions, if any, of the oxides Na2O, MgO, Al2O3, SiO2, P4O10, SO2 and SO3 with water including the likely pHs of the solutions obtained
9.2.4
describe, explain, and write equations for, the acid/base behaviour of the oxides Na2O, MgO, Al2O3, P4O10, SO2 and SO3 and the hydroxides NaOH, Mg(OH)2 and Al(OH)3 including, where relevant, amphoteric behaviour in reactions with acids and bases (sodium hydroxide only)
9.2.5
describe, explain, and write equations for, the reactions of the chlorides NaCl, MgCl2, AlCl3, SiCl4, PCl5 with water including the likely pHs of the solutions obtained
9.2.6
explain the variations and trends in 9.2.2, 9.2.3, 9.2.4 and 9.2.5 in terms of bonding and electronegativity
9.2.7
suggest the types of chemical bonding present in the chlorides and oxides from observations of their chemical and physical properties

9.3 Chemical periodicity of other elements

9.3.1
predict the characteristic properties of an element in a given group by using knowledge of chemical periodicity
9.3.2
deduce the nature, possible position in the Periodic Table and identity of unknown elements from given information about physical and chemical properties