The Periodic Table

• In the early 1800s, scientists had no understanding of atomic structure or of protons or electrons, so there was no such thing as an atomic number to them.

  Back then, the only thing they could measure was atomic mass.

  As a result, the known elements were originally arranged in order of atomic weight.
• John Newland was the first to attempt to arrange the elements in a table. He also ordered the elements in atomic weight but didn't think much of the elements being placed with other elements with similar properties. But his table had some flaws:

  • Some of his groups contained elements that didn’t have similar properties, e.g. carbon and titanium.
  • He mixed up metals and non-metals in his groups, E.g. oxygen (a non-metal) and iron (a metal) were in the same group.
• Dmitri Mendeleev came the closest to our modern day periodic table.

  He decided to order them in terms of their properties, putting similar elements in the same column.

  Where Mendeleev really succeeded was that he left GAPS.

  Where there was not an element to go with the pattern of properties Mendeleev just left a gap, suggesting that more elements would be discovered.