Atomic Structure

Atomic Structure

1. Atoms , elements and compounds

   • all substances are made of atoms
   • an atom is the smallest part of an element that can exist
   • an element is a substance made up of atoms with the same atomic number
   • compounds contain two or more elements chemically combined in fixed proportions
     • compounds are formed from elements by chemical reactions, which always involve the formation of one or more new substances, and often involve a detectable energy change

2. Mixtures

   • a mixture consists of two or more elements or compounds not chemically combined together - the chemical properties of each substance in the mixture are unchanged.
   • mixtures can be separated by physical processes
     • chromatography - separates