Changes

: 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 how to correct '''Mendeleev's Periodic Table'''by ordering the [[element]]s by [[Atomic Number]] instead of [[Relative Atomic Mass]]. This produced the modern [[Periodic Table]].