The periodic table and transition metals GapFill

In the periodic table, elements are ordered by their  hardnessreactivityconductivityatomic massatomic numbercolour. Columns in the periodic table are called  setsperiodsclassesseriesgroupselemental regions, and all the elements in the same column have similar reactions because they have the same number of  protonsneutronsionselectronsisotopesatoms in their outer shell. Over time, new ways of organising elements have been invented. Elements were first put in order by atomic weight, but some elements were in the wrong group.  Ernest RutherfordLinus PaulingMax PlanckAlfred NobelDmitri MendeleevIsaac Newton changed the order and left gaps for  magneticundiscoveredradioactiveunreactivedangeroususeless 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  alloyssaltsionsnon-metalscarbonatesnoble gases. Group 0 elements are known as the  alkali gasestransition gasesunreactantsnoble gasesneon gasesnon-metallic gases and do not usually react. Their boiling point increases down the group. Group 1 elements are called the  alkali metalsmetallogensmetalliumsmicrometalsnoble metalsreactant metals and react with oxygen, chlorine and water. Their reactivity increases down the group. Group 7 elements are known as the halogens. A more reactive halogen  displacessolidifiesdissolvesovercomesreplacesincorporates less reactive halogens in a solution.