Development of the Periodic Table

• Periodic table


  Arranged into columns called groups
• Groups in the periodic table

  • Group 1
  • Group 2
  • Transition elements
  • Group 3
  • Group 4
  • Group 5
  • Group 6
  • Group 7
  • Group 0
• Periodic


  Occurring at regular intervals
• Elements in a group

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


  Groups of three elements with similar chemical properties
• Triads


  • Lithium, sodium, potassium
  • Chlorine, bromine, iodine
• Law of octaves


  Every eighth element reacts in a similar way
• Newland's law of octaves had problems as it did not always group elements correctly</b>
• Mendeleev's 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
  • Includes group 0 noble gases
• Ordering by atomic weight can put elements in the wrong groups due to isotopes