The periodic table and transition metals GapFill

In the periodic table, elements are ordered by their  atomic numbercolouratomic masshardness. Columns in the periodic table are called  groupsclassesperiodssets, and all the elements in the same column have similar reactions because they have the same number of  protonselectronsionsatoms 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 RutherfordDmitri MendeleevLinus PaulingAlfred Nobel changed the order and left gaps for  undiscoveredunreactivedangeroususeless 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  saltsionsnon-metalsnoble gases. Group 0 elements are known as the  transition gasesnoble gasesalkali gasesnon-metallic gases and do not usually react. Their boiling point increases down the group. Group 1 elements are called the  alkali metalsmetallogensnoble metalsmetalliums 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  incorporatesdisplacesreplacessolidifies less reactive halogens in a solution.

 MetamorphicConversionAlkaliTransition metals are in the central block of the periodic table. They are metals, but they have very different chemical and physical properties from the metals in Group 1. For example:

• they are  more fluidmore reactivemore stableharder
• they change state at a higher temperature, so have higher melting points
• their strength is higher, so they are often used in construction
• they react less vigorously with oxygen,  waterbasessulfurcarbon dioxide and halogens

They can often be used as  endothermsreagentscatalystssolvents to speed up reactions. They can also form  electronicreflectivecovalentcoloured compounds, and have ions with different  chargesshapesnumbers of protonsmagnetic properties.