MEPX
Chapter 2 of 10All chapters
  1. 1Atoms
  2. 2The periodic table
  3. 3Bonding
  4. 4Reactions
  5. 5Acids and bases
  6. 6States of matter
  7. 7Mixtures and separation
  8. 8Organic chemistry
  9. 9Chemistry around you
  10. 10Working safely

Chapter 2 of 10

The periodic table

An arrangement that predicts behaviour.

Reading it

Rows are periods, filling successive electron shells. Columns are groups, sharing the same number of outer electrons, which is why they behave alike.

  • Group 1 metals are violently reactive; group 18 noble gases barely react at all.
  • Mendeleev left gaps and correctly predicted the properties of elements not yet found.

Trends

Atomic size, reactivity and the tendency to gain or lose electrons vary smoothly across the table. The layout is a map of behaviour, not a filing system.