Electron shells

Electron shells

1. How to work out the electron structure

   • 1). The periodic table tells us potassium has 19 electrons.
     • 2). Following the rules. The 1st shell uses two electrons and the 2nd, 3rd and 4th can have a maximum of 8 electrons.
       • 3). So the electron structure for potassium is 2,8,8,1

2. Rules

   • 1). Electrons always occupy shells (sometimes called energy levels).
     • 2). The lowest energy levels are always filled first these are the ones closest to the nucleus.
       • 3). Only a certain number of electrons are allowed in each shell: 1st shell = 2 electrons, 2nd+3rd...=8 electrons.
         • 4). Atoms are happy with a full outer shell like the noble gases.
           • 5). In most atoms, their outer shell isn't full and this makes an atom react to fill it.

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