Electron Shells

Electron shells always occupy shells somtimes calles energy levels

the lowest levels are always filled with energy first

only a certain number of electron are allowed in each shell 1st: 2 2nd 8 3rd 8

atoms are much happier when they have full electron shells 

In most atoms the outer sheel is not full and this makes the atom want to react.

An elements electron arrangment determines its chemical properties 

You need to know the electron configuration for the first twenty elements in the periodic table. 

H = 1                                                                                             He = 2

Li = 2,1     Be = 2,2   B = 2,3      C = 2,4    N= 2,5  O = 2,6   F = 2,7   Ne = 10

Na = 2,8,1  Mg = 2,8,2  Al = 2,8,3   Si= 2,8,4  P= 2,8,5  S= 2,8,6 CL = 2,8,7  Ar = 2,8,8

K = 2,8,8,1    Ca = 2,8,8,2