<P> Shortcomings of Mendeleev's table </P> <Ul> <Li> The table was not able to predict the existence of the noble gases, but did, however, leave spaces for yet to be discovered elements to slot into . Time proved this audacious calculation correct . However, when this entire family of elements was discovered, William Ramsay was able to add them to the table as Group 0, without the basic concept of the periodic table being disturbed . </Li> <Li> A single position could not be assigned to hydrogen, which could be placed either in the alkali metals group, the halogens group or separately above the table between boron and carbon . </Li> <Li> The lanthanides were difficult to fit into the table . </Li> <Li> Polonium and radium, discovered by Marie Curie in 1898, also were difficult to fit into the table . </Li> </Ul> <Li> The table was not able to predict the existence of the noble gases, but did, however, leave spaces for yet to be discovered elements to slot into . Time proved this audacious calculation correct . However, when this entire family of elements was discovered, William Ramsay was able to add them to the table as Group 0, without the basic concept of the periodic table being disturbed . </Li> <Li> A single position could not be assigned to hydrogen, which could be placed either in the alkali metals group, the halogens group or separately above the table between boron and carbon . </Li>

Who invented the modern periodic table of elements