1. The elements are arranged by energy levels, valence electrons, what group its on (Alkali Metals, Alakine Earth Metals, Boron Family, etc.), and forms ( metals, nonmetals, metalliods).
2. The periodic table tells scientists how reactive an element is, if it is a metal, nonmetal, or metalliod, and what group it's in.
3. Every element in a group has the same number of valance electrons ( They all have the same reactivity).
4. Where is the chart? I can't view it if it is there.