Periodic Table


All substances, both living and non-living, are composed of matter

The fundamental unit of matter is the atom, which consists of:

  • Protons (+ve charge) and neutrons (no charge) within a central nucleus
  • Electrons (–ve charge) circling the nucleus in regions called orbitals

Different atoms will possess different chemical properties (how they react)

Atoms can be grouped by properties and displayed according to a periodic table

Periodic Table of Elements

periodic table

Atoms in the same group (columns) 
share chemical properties as they have the same number of electrons in their outer shell

Atoms in the same period (rows) have the same number of electron shells but do not share any consistent chemical properties

Atoms always have the same number of protons and electrons - when they gain or lose electrons they become charged ions

An atom may have a different number of neutrons - these different forms are called isotopes and can cause radioactive decay