The periodic table GapFill

In the periodic table, elements are ordered by their  atomic massconductivityatomic numberreactivity. Columns in the periodic table are called  elemental regionsperiodsgroupsseries, and all the elements in the same column have similar reactions because they have the same number of  isotopeselectronsneutronsprotons in their outer shell. Over time, new ways of organising elements have been invented. Elements were first put in order by  atomic weighthow common they werenumber of isotopesdiameter, but some elements were in the wrong group.  Isaac NewtonMax PlanckErnest RutherfordDmitri Mendeleev changed the order and left gaps for  unreactivemagneticradioactiveundiscovered elements, based on the chemical properties of the elements.

Elements which form positive ions when they react are called metals, and elements which do not form positive ions when they react are called  saltscarbonatesalloysnon-metals.