The smallest component of an element 

Number of protons in the nucleus 

Protons plus neutrons 

Region of negativly charge surrounding the an atomic nucleus 

Very reactive elements that are in group 1 of the periodic table

Reactive elements in group 2 of the periodic table

Metallic elements in groups 4-12 on the periodic table

Reactive non-metals in group 17 of the periodic table

Gaseous elements in group 18 on the periodic table.