C1

• Atom


  Smallest unit of an element that retains its properties
• Element


  A substance made up of only one type of atom
• Mixture


  Two or more elements or compounds that are not chemically combined
• Compound


  A substance made up of two or more different elements chemically combined in fixed proportions
• Separating mixtures

  1. Filtration

  2. Crystallisation

  3. Simple distillation

  4. Fractional distillation

  5. Chromatography
• The components of a mixture retain their own properties
• Mixtures can be separated by physical processes, not chemical reactions
• The total mass of the products of a chemical reaction is always equal to the total mass of the reactants
• The products of a chemical reaction are made from exactly the same atoms as the reactants
• Atoms contain three types of subatomic particle: protons, neutrons and electrons
• Atomic number


  The number of protons in the nucleus of an atom
• Mass number


  The sum of the protons and neutrons in the nucleus of an atom
• Isotope


  Atoms of the same element with the same number of protons but different numbers of neutrons
• Atoms have no overall charge because they contain an equal number of protons and electrons
• All atoms of a particular element have the same number of protons
• Atoms of different elements have different numbers of protons
• The number of neutrons in an atom is equal to the mass number minus the atomic number
• Electron configuration


  The arrangement of electrons around the nucleus of an atom
• The first shell can only hold a maximum of 2 electrons, and the next two shells can each hold a maximum of 8 electrons
• Periodic table


  Arrangement of elements in order of increasing atomic number
• Group


  Vertical column in the periodic table containing elements with similar properties
• Transition metals


  Elements in the centre of the periodic table, between Groups 2 and 3
• Transition metals


  • Form coloured compounds
  • Have ions with different charges
  • Can be used as catalysts
  • Good conductors of heat and electricity
  • Can be easily bent or hammered into shape
• Group 0 (noble gases)

  • Have a full outer shell of electrons
  • Very stable and unreactive
• Group 1 (alkali metals)


  • Have one electron in their outermost shell
  • Have low melting and boiling points that decrease down the group
  • Become more reactive down the group
  • React vigorously with oxygen and water
• Group 7 (halogens)


  • Have seven electrons in their outermost shell
  • Exist as molecules made of pairs of atoms
  • Reactivity decreases down the group
  • Higher relative molecular mass, melting point and boiling point down the group
  • React with metals to produce ionic salts
• More reactive halogen


  Displaces the less reactive halogen from aqueous solution of its salt