Lesson 2: Quantum Numbers

• Electron Configuration


  The distribution of electrons of an atom
• Orbital

  • s
  • p
  • d
  • f
• Subshell

  • 1 subshell contains 2 electrons
  • p contains 6 electrons
  • d contains 10 electrons
  • f contains 14 electrons
• Electrons move very quickly
• How to fill electron shells

  1. Electron configuration

  2. Using shells to indicate where the electrons are at any moment
• Atomic number


  Number of protons
• Isoelectric


  They have the same number of electrons
• Electron Configuration Trends in the Periodic Table

  • Transition metals: d-block
  • Actinoids and lanthanoids: f-block
  • Metalloids and non-metals: p-block
  • Alkali and alkaline earth metals: s-block
• Transition metal shells can empty in different ways
• Quantum Numbers

  • Principle Quantum Number (n)
  • Orbital Shape Quantum Number (l)
  • Magnetic Quantum Number (ml)
  • Spin Quantum Number (ms)
• Principle Quantum Number (n)

  • Positive whole numbers (1, 2, 3...)
  • Specifies energy level
  • Higher n = higher energy level = larger orbital radius
  • Maximum number of electrons in a level = 2n2
• Orbital Shape Quantum Number (l)

  • Also known as the angular momentum quantum number
  • Describes the orbital shape
  • Ranges from 0 to n - 1
  • Each l value corresponds to a letter
• Magnetic Quantum Number (ml)

  • Orientation of the orbital in space
  • Ranges from -l to +l
  • For each l there are 2l + 1 ml values
• Spin Quantum Number (ms)


  • Property of an electron
  • Only 2 values → +1/2 & -1/2
  • +1/2 is an up spin
  • -1/2 is a down spin
• The total number of orbitals in a given n level is n2
• Up spin is always first
• Can't have 4 of the same quantum numbers
• Always start with negatives when listing ml
• Do all up spins first before the down spins
• s is l=0, p is l=1
• Orbital shape quantum number for each orbital

  s = 0

  p = 1

  d = 2

  f = 3