# Notes: Electron Configuration

```Electron Configurations
Schrodinger’s Quantum Model
 Principal Energy Levels - A region around the nucleus of an
atom where the electron is likely to be moving.
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The principal energy levels (n) are assigned values in order of
increasing energy
The average distance of the electron from the nucleus increases with
increasing energy levels. (1 is closest to nucleus.)
There are 7 energy levels = 7 periods.
Energy Sublevels
 Energy sublevels can be thought of as a section of seats in a theater. The rows
that are higher up and farther from the stage contain more seats, just as energy
levels that are farther from the nucleus contain more sublevels.
 The number of energy sublevels is the same as the number of principal energy
levels. 7
 Sublevels are labeled __s___ , ___p__ , __d___ , and __f___according to the
shapes of the atom’s orbitals
Atomic Orbitals
 Atomic orbitals represent the electron probability clouds of an
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atom’s electrons.
Each orbital may contain at most ____2____ electrons.
All s orbitals are spherical
All p orbitals are dumbbell-shaped
4 out 5 d orbitals are flower-shaped and one has a unique
shape
7 f orbitals have different and very complex shapes
 Shortcuts – Noble Gas Notation method – used to
represent electron configurations of noble gases using
bracketed symbols.
 Practice:
 Use shortcut method to write e-configurations for Ar and P.
 Ar: [Ne] 3s2 3p6 or [Ar]
 P: [Ne] 3s2 3p3
Ground State vs. Excited State
 Ground State – The most stable, lower energy
arrangement of the electrons in an atom.
 (The electrons are in the correct order of orbitals.)
 Excited State – When atom gains energy the electrons
jump into higher energy level.
 Identify the following atoms and describe their state.
(Ground or Excited)
 1s22s22p63s23p64s13d104p3
 1s22s22p63s23p64s23d104p5
 1s22s22p63s23p64s23d104p65s24d8
Electron Configuration – How to show
the arrangement of electrons
Aufbau Principle – Electrons enter orbitals of lower energy first.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p
Energy Level Increase
Pauli Exclusion Principle – No more than __2______ electrons can
occupy the same orbital AND they must spin in opposite direction
(Opposite spins help hold e- in an orbital by creating magnetic
attraction.)
Hund’s Rule – Orbitals of equal energy must EACH have _1____
electron with the same ____spin______ before any orbital is
occupied by a 2nd electron.