Changes

: A In 1808 a scientist called John Dalton, who created the [[Dalton Model]] of the [[atom]], arranged [[element]]s by their [[Relative Atomic Mass]].: A In 1864 a scientist called John Newlands arranged [[element]]s by [[Relative Atomic Mass]] but because he noticed that ever 8th [[element]] had similar [[Chemical Property|chemical properties]] he arranged them into what he called 'octaves'. However, he had not taken into account the possibility that some [[element]]s had not been discovered, so he placed some [[element]]s into the wrong groups just to fit the pattern he thought he had seen. : In 1869 [[Mendeleev]] was the first to place gaps where the [[element]]s did not fit the pattern but still arranged them by both their [[Chemical Property|chemical properties]] and [[Relative Atomic Mass]]. This enabled [[Mendeleev]] to [[Prediction|predict]] the existence of [[element]]s that had not yet been discovered.: '''Mendeleev's Periodic Table''' was proven (nearly) correct when new [[element]]s were discovered that fit in the the gaps he had left. This ability of his table to predict the [[property|properties]] of new [[element]]s was what convinced other scientists his [[Periodic Table]] was (nearly) correct.: There were some problems with '''Mendeleev's Periodic Table''' that kept scientists skeptical of it. One such problem was that [[Argon]] has a greater [[Relative Atomic Mass]] than [[Potassium]] which would put [[Argon]] in the [[Alkali Metal]]s.: Once the structure of the [[atom]] was investigated by physicists in the early 1900s it was discovered that how to correct '''Mendeleev's Periodic Table''' was not entirely correct and so the modern [[Periodic Table]] was created which ordered by ordering the [[element]]s by [[Atomic Number]] instead of [[Relative Atomic Mass]]. This produced the modern [[Periodic Table]].