Newlands
Newlands noticed that every eighth element has similar properties so he listed some of the known elements in rows of seven. These sets of eight were called Newlands octaves but unfortunately the pattern broke down after the third row with transition metals messing it up. It was because he left no gaps why his ideas were ignored. Newlands ideas were ignored because:
- His groups contained elements that didn't have somilar properties
- He mixed up metals and non-metals
- He didn't leave any gaps for undiscover elements
Mendeleev
In 1869, a russian scientist called Dmitri Mendeleev, arranged about 50 elements as shown in the picture. like Newlands he arranged elements in order of atomic mass but crucially mendeleev left gaps for undiscoverd elements. Also he found he had to leave gaps to keep elements with similar properties together.
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