This guide covers IGCSE Chemistry topic 9: the Periodic Table. You will revise groups (vertical; same number of outer electrons) and periods (horizontal; same number of shells), trends (metallic character, reactivity in Groups I and VII), and properties of metals and non-metals.

Key concepts to revise

• Group – Vertical column; same number of outer electrons; similar properties (e.g. Group I: alkali metals; Group VII: halogens).
• Period – Horizontal row; same number of shells; atomic number increases.
• Trends – Down Group I: reactivity increases (outer electron further from nucleus; easier to lose). Down Group VII: reactivity decreases (harder to gain electron; atom larger).
• Metals vs non-metals – Metals: left; lose electrons; form cations; basic oxides. Non-metals: right; gain electrons; form anions; acidic oxides.

Exam tips and command words

• State – The group number from the number of outer electrons; the period from the number of shells.
• Describe – The trend in reactivity down Group I (increases) and Group VII (decreases).
• Explain – Why reactivity increases down Group I (outer electron further; easier to lose).
• Compare – Properties of Group I and Group VII (metals vs non-metals; lose vs gain electrons).

Common mistakes

• Saying Group VII reactivity increases down the group (it decreases; atom larger; harder to gain electron).
• Confusing group (column) with period (row).
• Not stating that outer electrons determine chemical properties (same group = same number of outer electrons).

Revision checklist

• State the group and period of an element from its atomic structure (outer electrons, shells).
• Describe the trend in reactivity down Group I and Group VII and explain why.
• Compare metals and non-metals (position, electrons, type of oxide).
• State the number of outer electrons for Group I, II, VII, 0 (noble gases).

Next steps

Book a free trial with an IGCSE Chemistry tutor to practise Periodic Table questions, or explore Tutopiya’s learning portal for more revision resources.