Atomic Orbitals & Quantum Numbers

• The discrete lines observed in atomic spectra can be explained if electrons, like photons, also display the properties of both particles and waves.
• Electrons behave as standing (stationary) waves in an atom. These are waves that vibrate in time but do not move in space. There are different sizes and shapes of standing wave possible around the nucleus, known as orbitals. Orbitals can hold a maximum of two electrons.
• The different shapes of orbitals are identified as s, p, d and f.
• Electrons within atoms have fixed amounts of energy called quanta.
• It is possible to describe any electron in an atom using four quantum numbers:

  • The principal quantum number n indicates the main energy level for an electron and is related to the size of the orbital.
  • The angular momentum quantum number l determines the shape of the subshell and can have values from zero to n −1.
  • The magnetic quantum number ml determines the orientation of the orbital and can have values between −l and +l.
  • The spin magnetic quantum number ms determines the direction of spin and can have values of +1/2 or -1/2.