ELECTRON CONFIGURATIONS

=Electron Configurations (up to Atomic Number 20)= ===Electrons are arranged into shells or layers, known as energy levels...=== *The first shell only fits ''TWO'' electrons *The second shell fits ''EIGHT'' electrons *The third shell can fit ''EIGHT'' electrons *Electrons then begin to fill the fourth shell E.g. Calcium has 20 electrons. The electron configuration of a Calcium atom is: 2, 8, 8, 2 [image:http://i.imgur.com/gu9Jo3k.png?1] If you look closely at the electron configurations above you will notice that... *elements in the same group have the same number of valence (outer shell) electrons *elements in the same period (row) have the same number of energy levels / shells