Nature of chemical reactions and substances

• Atoms


  Smallest particles of elements. Not possible to split into anything smaller. Contains a central nucleus with orbiting electrons (in cells)
• Molecules


  Groups of atoms chemically bonded. Atoms joined in fixed ratios having specific formula. There can be molecules of elements and molecules of compounds.
• Ions


  Charged particles. Formed when atoms gain or loose an electron. Loose=positive gain=negative. Size of the charge is equal to the number of electrons gained or lost.
• How is matter classed?

  Elements, compounds, or mixtures
• Elements


  Basic building blocks of all substances. Cannot be broken down into simpler substances. Each element is made up of one atom.
• Compounds


  Substances that contain 2 or more elements chemically joined. Compounds have different properties from the elements that make them up. Elements joined in fixed ratio's represented by the formula.
• Mixtures


  Made from two different substances that aren't chemically joined . Mixtures can be made from different elements or compounds mixed together. Separated by physical techniques eg filtration, distillation and chromatography.
• Elements molecules

  Each molecule is the same. Made from one type of atom.
• Compound molecules


  Each molecule is the same. 2 different atoms chemically joined.
• Mixtures molecules


  2 different molecules present. Not chemically joined.
• Chemical symbols


  Shorthand way of representing elements. Consists of 1 or 2 symbols. First letter uppercase Second letter lowercase (If it has one).
• Chemical formula


  Shorthand way of writing compounds. Shows the names of elements and amount of elements.
• Writing ionic formula


  When non metals react with metals they form ionic formula. 1. identify ions 2. cancel out charges 3. Construct