Why do atoms need 8 electrons to stabilize?
The valence orbitals of atoms are composed of suborbitals (s and p)  there is 1 s suborbital which is spherical and can hold 2 electrons (one with up spin and one with down spin). There are 3 p suborbitals which are dumbbell shaped (look like two balloons tied together at the ends) and align along the x,y&amp;z axies and hold a total of 6 electrons (2 per axis, 3 with up spin and 3 with down spin).  Since an atom is energetically satisfied when all of the electrons are paired and 2+6 = 8, an atom must have 8 electrons in its valence shell to pair all of the electrons.

The octet rule does not apply to all atoms though, for transition metals and later elements there is a d suborbital which can hold an addition 10 electrons, meaning that now an atom may have 18 electrons in its valence shell to be satisfied.  This allows for materials such as metal complexes and the sulfate poly-atomic-ion to exist despite having more than eight electrons in the valence shell.