development of the periodic table

• mendeveel arranged the elements in mass order, grouping together elements with similar properties. left gaps for undiscovered ones
• 118 elements in total
• metals to the left of the stepped line
• non metals to the right
• vertical is down and horizontal is side ways
• group 2 elements - from top to bottom melting point decreases, hardness decreases and reactivity increases
• group = down and period is across
• can test for the gas hydrogen

  • holding a burning splint held at the open end of a test tube of gas
  • If the gas is hydrogen it burns with a loud “ squeaky pop