Electronic Structure

• The fact that electrons occupy 'shells' around the nucleus is what causes the whole of chemistry
• Electrons always occupy shells (sometimes called energy levels)
• The lowest energy levels 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
  • Other shell = 8
• Atoms 'want' to 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
• E.g. What is the electronic structure of nitrogen?

  1. Nitrogen's atomic number is 7. This means it has 7 protons... so it must have 7 electrons
  2. So the electronic structure for nitrogen is 2, 5