Development of the periodic table

• Periodic table


  Arrangement of elements into a table where elements with similar properties occur at regular intervals
• Groups in the periodic table

  • Group 1
  • Group 2
  • Transition elements
  • Group 3
  • Group 4
  • Group 5
  • Group 6
  • Group 7
  • Group 0
• Elements in a group

  • Have the same number of electrons in their outer energy level
  • Have similar chemical properties and react in a similar way
• Triads


  Groups of three elements with similar chemical properties
• Newland's law of octaves

  1. Arrange elements in order of increasing atomic weight

  2. Every 8th element reacts similarly
• Mendeleev's periodic table


  • First modern periodic table
  • Arranged elements in order of increasing atomic weight
  • Switched order of specific elements to fit patterns
  • Left gaps for undiscovered elements
• Mendeleev's predictions of undiscovered elements were correct
• Modern periodic table


  • Arranged in order of atomic number (number of protons)
  • Includes group 0 (noble gases)
• Ordering by atomic weight can put elements in the wrong group due to isotopes