Electronic Structure

• Electron state of motion

  Electrostatic field created by the nuclei of an atom
• Neil Bohr's description of the atom


  • Having energy levels where the electron resides around a nucleus
  • Energy level as an orbit and each orbit has specific energy level
• Energy levels


  Levels of energy which atoms move between when they gain or lose electrons
• Space where electrons move around the nucleus

  • Divided into principal energy levels, sublevels, and orbitals
• Principal Energy Level


  • Designated by quantum number "n" and numbered 1,2,3...
  • The energy level closest to the nucleus has a value of n=1 and increases as it moves farther
  • Maximum number of electrons in each principal energy level solved using 2n^2
• Sublevels


  • Principal energy levels can further be divided into sublevels denoted by s,p,d,f,g, h, i
  • If there's only 1 sublevel, it is labeled as s, for 2 sublevels it is labeled as s and p
• Orbitals


  • A region that represents the location where electrons are most likely to be found
  • Each orbital can hold up to a maximum of 2 electrons
  • Each sublevel has a corresponding number of orbitals and hence the number of electrons
• Electronic Configuration


  A shorthand notation to determine the principal energy level, sublevel, and orbital that electrons occupied in elements
• Valence Electrons


  • Electrons in the outermost shell
  • Number of valence electrons = number of electrons in the principal energy level
  • For family A elements, valence electrons = group number
  • The highest principal energy level is the period
• Pauli Exclusion Principle


  • There should only be 2 electrons that must occupy each orbital, one spinning up and the other spinning in the opposite direction
• Hund's Rule


  • The pairing up of electrons does not start until all of the orbitals in the same sublevel have at least one electron each, to avoid repulsion between electrons
• Aufbau Principle


  • The stability of electrons in the orbital is determined by their attraction to the nucleus
  • Electrons should occupy the orbitals in the lowest energy levels first and fill it up as the energy increases
  • Electrons should occupy orbitals of equal energy so that all sublevels contain one electron each before pairing up
  • Two electrons can occupy an orbital if they have an opposite spin
  • The maximum number of electrons per orbital is 2