AQA GCSE Chemistry · 8462
Specification 4.1.2.1 · Paper 1, Paper 2
A horizontal row of the periodic table.
Revise: Periodic Table OrganizationA horizontal row is a period. The period number tells you the number of occupied electron shells in an atom. For example, an atom with the electronic structure 2,8,2 has electrons in three shells, so its element is in Period 3.
- Revise: Atomic Structure and the Periodic Table
A horizontal row of the periodic table; for the first 20 elements, its number equals the number of occupied electron shells.