Electronic Configuration

•The type of code that describes how many electrons are in each level (energy) of an atom and how the electrons are arranged with each level.

•The wave function predicts a three dimensional region around the nucleus called the atomic orbital.

When n = 1 , then ℓ = 0

this shell has a single orbital (1s)to which 2e- can be assigned.

When n = 2 , then ℓ = 0,1

   2s orbital                 2e-

   three 2p orbital      6e-

   TOTAL                      8e-

When n = 3 , then ℓ = 0,1,2

   3s orbital                 2e-

   three 3p orbital      6e-

   five 3d orbital         10e-

   TOTAL                      18e-

When n = 4 , then ℓ = 0,1,2,3

   4s orbital                  2e-

   three 4p orbital       6e-

   five 4d orbital         10e-

   seven 4f orbital      14e-

   TOTAL                      32e-

•The Aufbau principle – states that electron occupies the lowest energy orbital available.

•The Pauli exclusion principle – states that a maximum of two electrons can occupy a single orbital, but only if the electrons have the opposite spins.

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•Hund’s rule – states that single electrons with the same spin must occupy the same level orbitals.

Valence Electron and Electron Dot Structure

•Valence electron are defined as electrons in the atoms outermost orbital – those associated with the atom’s highest principal energy level.

•Electron - dot structure consists of the element’s symbols representing the nucleus, surrounded by dots representing the elements valence electrons.

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