ELECTRONS SHELLS

ELECTRONS SHELLS

1. ELECTRON SHELL RULES

   • Electrons always occupy shells [Sometimes called energy levels]
   • The inner shells are always filled first- these are the ones closest to the nucleus
   • Only a certain number of electrons are allowed in each shell
     • 1st shell: 2/ 2nd shell: 8/ 3rd shell: 8
   • Atoms are positive when they have full electron shells- like noble gases in GROUP 0
   • In most atoms the outer shell is not full and this makes the atom want to REACT to fill it

2. Electronic Structure

   • If for example nitrogen has seven protons, it should also have seven electrons
   • The FIRST shell, can only take 2 electrons and the second shell can take a maximum of 8 electrons
   • So the electronic structure for nitrogen must be 2,5