Electron Configuration

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Electron Configuration

• Peg Ellis

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INTRODUCTION
Modern Atomic View The world of the atom is
made up of waves and probability, The speed and
location are subject to uncertainity.
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ELECTRON ORBITALS
Heisenberg Uncertainty Principle
It is impossible to know with certainity both the
location and the velocity of an electron.
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Bohr Diagrams
Diagrams are useful for counting electrons and
illustrating different energy levels. Worthless
as pictures of what atoms really look like.
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This solar system model uses orbits To show where
the electrons are. Electrons do not orbit the
nucleus. They live in regions of space
called Orbitals. Orbitals are organized by the
energy level or shell that they belong to. They
are clouds of probability.
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An orbital is the shape of the region of space
where an electron is most likely to be found.
This ball-shaped orbital is hydrogen. The dots
represent possible positions of the one electron
hydrogen has.
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Notice there are more dots near the center of
sphere than near the edges.
1s orbital
ANALOGY Bird feeder on a pole with birds
migrating south surrounding the feeder. Blue
spots could be a bird at any given time.
Spherical shape
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2s Orbital
Also shaped spherical. The difference Larger and
higher energy than the 1s orbital.
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SHAPES OF ORBITALS

• 2s orbital 2p orbital 3d
  orbital

Spherical double lobed complex There are
also f orbitals- very complex
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ENERGY LEVELS

• The more energy- the farther away the shell is
  from the nucleus

1st shellone type of orbital s 2nd shell two
types s,p etc.
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Principal Quantum Number

• The energy levels or shells are distinguished by
  their number.
• This number is called the principal quantum
  number.
• Each energy level have specific
• Names. N1 only 1s orbital
• N2 2s and 2p orbitals
• N3 3s, 3p, and 3d orbitals

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Energy Levels
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How many electrons can be in a sublevel?
Remember A maximum of two electrons can be
placed in an orbital.
s orbitals
d orbitals
p orbitals
f orbitals
Number of orbitals
1
3
5
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Number of electrons
2
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6
10
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ELECTRON RULES
Aufbau Principle from bottom up Hunds Rule
singles first Pauli Exclusion Principle
opposites only
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From the Bottom Up Rooms must be filled from the
ground floor up. Fill the one room on the first
floor before starting to put new tenants on the
second floor. Then fill the s room before the p
rooms. At higher floors the order might change a
bit. Aufbau Principle the electrons fill the
available orbitals from lowest energy to highest
energy. In the ground state all the electrons are
in the lowest possible energy level.
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Singles First the owner of the building wants
to have the tenants spread out as much as
possible. For that reason singles are placed in
rooms before couples. If couples must be
placed into a room then all of the other rooms on
that floor must already have a single in them.
Hunds Rule The electrons must be placed into
the orbitals in such a way that no pairs are put
together unless absolutely necessary. That is,
single electrons must be placed into boxes first
and then paired up if necessary.
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SHORTHAND NOTATION

• 1s2 1 quantum number
• (energy level)
• s s- type orbital
• 2 electrons
• 2p6 2nd quantum number,
• p type orbital,
• 6 electrons

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Electron Configurations

• 2p4

Number of electrons in the orbital
Energy Level
Orbital
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2
4f14 etc.
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Electron Configuration Order
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Notice that 4s orbital fills Before the 3d
orbital. This is because 4s is actually slightly
lower in energy than the 3d orbitals.
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Arrow direction Represents electron Spin.
Clockwise and counterclockwise
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What is the element? 1s22s22p63s23p64s23d104p65s1
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Rubidium 37 electrons
What is the element? Kr 5s1
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