Periodic Table IGCSE Chemistry: Complete Revision Guide

The periodic table sits at the heart of IGCSE Chemistry. Whether you sit Cambridge, Edexcel, or AQA, you will not get through the exam without understanding how the table is organised, what the trends mean, and how to apply to unfamiliar questions.

This guide covers every major periodic-table topic tested at IGCSE. Work through it section by section, and you will have a clear picture of what examiners expect and where students most often drop marks.

How is the periodic table structured?

The periodic table arranges all known elements by increasing atomic number, placing elements with similar chemical properties in the same vertical column. It organises over 100 elements into a format that reveals patterns in structure, bonding, and reactivity.

According to Cambridge International Education, the periodic table is a required topic across the IGCSE Chemistry syllabus. Understanding it unlocks a large share of the marks available across the multiple-choice and theory papers.

The table is divided into periods (horizontal rows) and groups (vertical columns). The period number tells you how many electron shells it has. The group number tells you how many electrons are in the outer shell, which determines how the element reacts.

The table contains three broad regions: metals on the left and centre, non-metals on the upper right, and a zigzag boundary of metalloids between them.

Periods

There are seven periods in the full table, and IGCSE students focus mainly on Periods 1, 2, and 3. As you move across a period from left to right, the atomic number increases by one each time.

Across a period, the number of protons increases, pulling electrons closer to the nucleus. This affects atomic radius, ionisation energy, and the type of bonding the element typically forms.

Groups

Groups are numbered 1 to 7, plus Group 0 (the noble gases). Elements in the same group share the same number of outer-shell electrons, which is why they have similar chemical properties.

For example, all Group 1 elements have one outer electron. They all react with water to produce a metal hydroxide and hydrogen gas, and the reactions become more vigorous down the group.

Electron configuration and key trends

Electron configuration

Electron configuration describes how electrons are arranged in shells around the nucleus. At IGCSE, you write these as numbers separated by commas, showing how many electrons occupy each shell.

The rules are straightforward. The first shell holds a maximum of 2 electrons; the second and third shells each hold a maximum of 8. So sodium (atomic number 11) has the configuration 2, 8, 1.

Our tutors regularly see students confuse the number of outer-shell electrons with the period number. Remember: the period tells you the number of shells, and the group tells you the number of outer electrons.

Configuration connects directly to bonding. Atoms with nearly full outer shells tend to gain electrons; atoms with one or two outer electrons tend to lose them. This drives ionic bonding, one of the most commonly tested concepts in IGCSE Chemistry.

Key periodic trends

Trend questions are among the most predictable in the exam. Examiners expect you to describe, explain, and sometimes compare trends using the correct chemical vocabulary.

Atomic radius increases down a group, because each new period adds an electron shell, pushing outer electrons further from the nucleus. It decreases across a period, as more protons pull the same shells inward more strongly.

Metal reactivity increases down a group: the outer electron is further out and more shielded, so it is lost more easily. Potassium is more reactive than sodium, which is more reactive than lithium.

Non-metal reactivity decreases down a group: the larger atom attracts electrons less effectively. Fluorine is the most reactive non-metal; iodine is the least reactive of the common halogens.

Melting and boiling points vary by group. In Group 1 they decrease down the group; in Group 7 they increase down the group. Knowing the direction of each trend and the reason behind it earns full marks.

The key groups: 1, 7, and 0

Group 1: the alkali metals

Group 1 elements are the alkali metals, including lithium, sodium, and potassium at IGCSE. All three are soft, shiny metals that react vigorously with water and must be stored under oil to keep them from air and moisture.

The reaction with water follows a consistent pattern: the metal forms a metal hydroxide and hydrogen gas, and it becomes faster and more energetic from lithium to potassium.

Examiners often ask you to predict the behaviour of rubidium or caesium from the lithium-to-potassium trend. Practise this style; it rewards students who understand the pattern, not just those who memorised individual facts.

Group 7: the halogens

Group 7 elements are the halogens: fluorine, chlorine, bromine, and iodine. They all have seven outer-shell electrons and react by gaining one electron to form a singly charged negative ion.

The key trend is displacement: a more reactive halogen displaces a less reactive one from a solution of its salt. Chlorine displaces bromide ions from potassium bromide, turning it orange-brown; bromine displaces iodide ions, turning the solution brown.

Physical state is also tested. Fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid. Down the group, melting and boiling points rise as molecules get larger and intermolecular forces strengthen.

Group 0: the noble gases

Group 0 contains the noble gases: helium, neon, argon, krypton, and xenon. They are colourless, odourless gases at room temperature and are almost entirely unreactive under normal conditions.

Their stability comes from their electron configuration: a full outer shell. Helium has 2 electrons in its only shell; the others have 8. With a full outer shell, an atom has no tendency to gain or lose electrons, so it stays unreactive.

Examiners use noble gases to test why a full outer shell equals stability, and to contrast that with the reactive behaviour of Group 1 and Group 7 elements.

Metals, non-metals, and transition metals

Most elements are metals, occupying the left and centre of the table, including the transition metals in the middle block. Non-metals sit to the upper right. The table below summarises the key differences tested at IGCSE.

Property	Metals	Non-metals
Electrical conductivity	Good conductors	Poor conductors (except graphite)
Melting point	Generally high	Generally low
Appearance	Shiny, lustrous	Dull (most)
Malleability	Malleable and ductile	Brittle when solid
Oxide character	Basic oxides	Acidic oxides
Ion formed	Positive ions (cations)	Negative ions (anions)

These differences link directly to bonding, structure, and reactivity. Metal oxides reacting with acids, for example, is a common six-mark question type that draws on this knowledge.

Transition metals

The transition metals occupy the central block, between Groups 2 and 3. Common IGCSE examples are iron, copper, zinc, and manganese. Unlike Group 1 metals, they are harder, have higher melting points, and are much less reactive with water.

They also form coloured compounds and can act as catalysts. A defining feature is variable valency: iron forms Fe2+ and Fe3+, and copper forms Cu+ and Cu2+. This produces the range of coloured compounds seen in qualitative analysis.

According to Cambridge International, questions on transition-metal properties and their use as catalysts appear regularly in the core and extended papers. Iron as the catalyst in the Haber process is the most commonly cited example.

How Talimat Can Help

Periodic-table questions reward students who understand patterns, not just those who memorise facts. That skill is built through practice, explanation, and feedback, and it takes time to internalise why the trends work as they do.

Talimat connects students with specialist IGCSE Chemistry tutors through live, 1:1 sessions. Every tutor holds a relevant degree in their subject. Students get a personalised study plan from day one and regular mock practice with written feedback.

An Academic Consultant is assigned from the start to keep progress on track. If your child finds the periodic table or any IGCSE Chemistry topic difficult, contact us to match them with a specialist tutor.

Whether you are starting Year 10 or sitting exams in weeks, the right support at the right time makes a measurable difference. Work through each group and trend until the logic feels automatic, and the marks follow.