Electronic structure

• Electronic structure


  A set of numbers to show how the electrons in an atom are arranged in shells, or energy levels
• Electrons in shells

  • electrons in atoms occupy energy levels, also called electron shells, outside the nucleus
  • different shells can hold different maximum numbers of electrons
  • the electrons in an atom occupy the lowest available energy level first
  • this is the shell nearest the nucleus
  • when this shell is full the electrons begin to occupy the next energy level
• • 1st energy level shell = maximum of 2 electrons
  • 2nd energy level shell = maximum of 8 electrons
  • 3rd energy level shell = maximum of 8 electrons
• Diagram

  • each shell is shown as a circle
  • each electron is shown as a dot or a cross
• Electronic structure and the periodic table

  • number of circles = period number
  • number of electrons in outermost shell = group number
  • total number of electrons in all shells = atomic number