What are the key periodic table trends I need to know for IGCSE Chemistry?

The periodic table tests pattern recognition, not memory. Knowing three core trends will cover the majority of exam marks.

The period number tells you how many electron shells an atom has. The group number tells you how many electrons sit in the outer shell. Those outer electrons, called valence electrons, control bonding and reactivity. Group 1 elements have one valence electron; Group 7 elements have seven. This is the key to balancing chemical equations in Cambridge IGCSE Chemistry.

Group 1 alkali metals become more reactive as you go down the group. The outer electron sits further from the nucleus and is more shielded, so it is lost more easily. Lithium reacts steadily with water; potassium reacts vigorously, producing a lilac flame. All reactions release hydrogen gas and form a metal hydroxide.

Group 7 halogens show the opposite trend. Reactivity decreases down the group. Smaller atoms higher up attract an incoming electron more strongly. Chlorine can displace bromine from solution; bromine can displace iodine. These displacement reactions appear on exam papers every year.

Transition metals sit between Groups 2 and 3. They have high melting points, high density, and form coloured compounds. They also act as industrial catalysts: iron in the Haber process, vanadium(V) oxide in the Contact process.

These three groups are the most frequently tested in structured and multiple-choice questions. A quick summary of the two most-tested reactivity trends:

• Group 1: reactivity increases down the group
• Group 7: reactivity decreases down the group
• Group 0 noble gases: essentially unreactive
• Transition metals: no simple reactivity trend

For A-Levels, these patterns deepen into atomic orbital theory and electronegativity. But at IGCSE level, mastering group position and valence electrons is enough to answer almost every periodic table question confidently.

If you want to work through past paper questions on these trends with a subject-specialist tutor, online tutoring with Talimat matches you with a vetted tutor in under ten minutes. For a more detailed breakdown of every group and reaction type, see our blog and the full guide linked above.