Reactivity

-the ease and speed with which an element combines, or reacts, with other elements or compunds.
-groups and families have similar reactivity.
.group 1-metal react violently with water
.group 18-gases that barelt react at all.

-# of protons=# of electrons=0 charge

-electrons orbit in "shells"
.1st shell can only fit 2 electrons
.2nd&3rd ring can fit 8 electrons
-atoms want their shells to be full.