Topic C1 - atomic structure and the periodic table

• in an element all the atoms are the same
• compounds contain two or more different elements chemically combined in fixed proportions
• mixtures have different elements or compounds but theyre not chemically combined
• isotopes are different forms of the element that have the same number of protons but have a different number of neutrons
• relative atomic mass


  average mass of all the isotopes that make up an element
• Molecule


  2 or more atoms held together by chemical bonds
• Filtration seperates an insoluble solid from a liquid
• crystallisation seperates a soluble solid from a liquid
• Atomic number=


  number of protons
• mass number=


  sum of protons and neutrons
• an element is a substance made up of atoms that all have the same number of protons in their nucleus