The early periodic table
- In the 19th century chemists were finding new elements almost every year and were trying to find patterns in their behaviour which would allow them to organise the elements and understand more about chemistry
- In 1864 John Newlands arranged the known elements in order of mass and noticed that every eighth element seemed similar and produced his table of octaves. He assumed that all the elements had been found even though chemists were still discovering new ones. His table only worked for the known elements up to calcium.
- In 1869 Dmitri Mendeleev arranged all of the 50 discovered elements in a table, placing them in the order of their atomic weights. Then he arranged them so that a periodic pattern in their properties could be seen. He also left gaps for elements that hadn't yet been discovered then used his table predict what their properties should be like. A few years later, new elements were discovered with properties that closely matched Mendeleev's predictions and he is now remembered as the father of the modern periodic table.
1 of 2
The modern periodic table
- When electrons, protons and neutrons were discovered in the early 20th century, the periodic table was arranged in order of atomic (proton) numbers. When this was done, all elements were placed in appropriate groups.
- The modern periodic table can be seen as an arrangement of the elements in terms of their electronic structures.
2 of 2