The periodic table: Atomic structure and the periodic table: Chemistry: GCSE (9:1)

• atomic number

  the number of protons in the nucleus of an atom

  
• atomic mass


  The average mass of all the isotopes of an element

  
• mass number


  the sum of the number of neutrons and protons in an atomic nucleus

  
• John Dalton's Atomic Theory


  believed that atoms could not be divided, but were rearranged in chemical reactions

  
• John Newland's periodic table

  noticed a repeating pattern every 8 elements and suggested elements were found in 'octaves

  
• Disadvantages of Newland's ideas

  The octaves only work for the first 20 elements.
• Order of elements on historic periodic table

  Elements were ordered by atomic weight

  
• Order of elements on modern periodic table

  Elements are ordered by atomic number

  
• Dmitri Mendeleev's ideas


  Ordered elements by atomic weight BUT changed the order/left gaps to keep elements with similar properties in the same collumn

  
• Advantages of Mendeleev's ideas

  He was able to predict the properties of elements in the gaps.

  
• Group


  A vertical column of elements with the same number of outer shell electrons

  
• Period

  A horizontal row of elements with the same number of electron shells

  
• Physical properties


  observed or measured characteristics of a substance. (e.g. colour, density)

  
• Chemical properties


  How a substance reacts with other substances.