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Periodic Table
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Periodic Table Showing 42 elements
LANTHANIDES 57 - 71 • Period 6 f-block
ACTINIDES 89 - 103 • Period 7 f-block
IGCSE EXAM SUCCESS
Electronic structure: Always write it in shells (2, 8, 8, 1). Noble gases have full outer shells → very stable.
Group 1 vs Group 7: Alkali metals become more reactive down the group. Halogens become less reactive down the group.
Metals vs Non-metals: Metals conduct electricity, are malleable & ductile. Non-metals are brittle and poor conductors (except graphite).
Reactivity Series: Potassium > Sodium > Calcium > Magnesium > Aluminium > Zinc > Iron > Copper (most reactive first).
QUICK REVISION QUIZ

Test your knowledge

What this experiment shows

The periodic table is arranged in order of proton number, and that order alone produces the repeating pattern the table is named for. The group number tells you how many electrons an atom has in its outer shell, and the period tells you how many shells are in use. Because chemistry is decided by outer electrons, elements in the same group behave alike - which is what makes the table a prediction tool rather than a list.

group number = number of outer-shell electrons

What you need

  • An interactive periodic table - click any element for its data
  • Nothing else: this is a reference tool

How it is done

  1. Find an element and read its proton number and relative atomic mass.
  2. Read off its group and period.
  3. Work out the electron arrangement and check it against the group.
  4. Compare it with the element above and below it in the same group.

What you should see

  • Group I, the alkali metals, get more reactive down the group.
  • Group VII, the halogens, get less reactive down the group.
  • Group VIII, the noble gases, have full outer shells and are unreactive.
  • Metals sit on the left, non-metals on the right, with a staircase between them.

Where marks are lost

  • Saying reactivity always increases down a group. It does for metals and decreases for non-metals.
  • Reading the relative atomic mass as the proton number. The proton number is the smaller one.
  • Calling the transition elements a group. They are a block, and their behaviour is different.
  • Forgetting that hydrogen does not fit neatly anywhere.

Questions students ask

Why do Group I metals get more reactive down the group?
The outer electron is further from the nucleus and better shielded, so it is lost more easily - and losing that electron is what the reaction is.
Why are the noble gases unreactive?
They already have a full outer shell, so they have nothing to gain by sharing, losing or gaining electrons.
What do elements in the same group have in common?
The same number of outer-shell electrons, so they react in the same way and form compounds with the same formulae.

Try these next

Written for Cambridge IGCSE Chemistry 0620 and CBSE Class 9-12 by Ajay Shekhawat, founder of MrChemCoach. Run the simulator above, then check yourself against the questions.