• Why don’t the electrons fall into the nucleus?
• Move like planets around the sun.
• In circular orbits at different levels.
• Amounts of energy separate one level from another.
Nucleus
Electron
Orbit
Energy Levels
• Further away from the nucleus means more energy.
• There is no “in between” energy EnergyLevelsIn
crea
sin
g e
ner
gy
Nucleus
First
Second
Third
Fourth
Fifth
• Energy is quantized. It comes in chunks.
• A quanta is the amount of energy needed to move from one energy level to another.
• Since the energy of an atom is never “in between” there must be a quantum leap in energy.
• Schrodinger derived an equation that described the energy & position of e- in an atom
• Things that are very small behave differently from things big enough to see.
• The quantum mechanical model is a mathematical solution.
• Has energy levels forelectrons.
• Orbits are not circular.
• It can only tell us theprobability of finding an electron a certain distance/space from the nucleus.
• The atom is found inside a blurry “electron cloud”
• An area where there is a greater chance of finding an electron.
• Draw a line or picture at 90 % probability positions
Atomic Orbitals
• Principal Quantum Number (n) = the energy level of the electron.
• Within each energy level the complex math describes several shapes (functions).
• These are called atomic orbitals.
• Regions where there is a high probability of finding an electron.
• S orbital
-Found in EVERY energy level.
-Spherical shaped
-holds 2 electrons
-Called the 1s, 2s, 3s, etc.. orbitals.
• P orbital
• Begins at 2nd energy level
• 3 different directions: X, Y, Z
• Each holds 2 electrons
• “dumbbell” shaped
P Orbitals
• D orbital
-Begins at the 3rd energy level
-5 different shapes
-Each can hold 2 electrons
• F orbital
-Begins at the 4th energy level
-7 different shapes
-2 electrons per shape
s
p
d
f
# of
shapes
Max
electrons
Starts at
energy level
1 2 1
3 6 2
5 10 3
7 14 4
First Energy Level
• only s orbital
• only 2 electrons
• 1s2
Second Energy Level
• s and p orbitals are available
• 2 in s, 6 in p
• 2s22p6
• 8 total electrons
Third energy level
• s, p, and d orbitals
• 2 in s, 6 in p, and 10 in d
• 3s23p63d10
• 18 total electrons
Fourth energy level
• s,p,d, and f orbitals
• 2 in s, 6 in p, 10 in d, ahd 14 in f
• 4s24p64d104f14
• 32 total electrons
• From fourth on not all the orbitals will fill up.
• You simply run out of electrons
• The orbitals do not fill up in a neat order.
• The energy levels start to overlap
• Lowest energy fill first.
Incr
easi
ng e
ner
gy
1s
2s
3s
4s
5s
6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
Notice how the 4d
energy > 5s energy;
4f energy > 5p
energy
• How e- are arranged.
• Aufbau principle- electrons enter the lowest energy first. *“electrons are lazy”+
• Difficulties occur because of the overlap of orbitals of different energies.
• Pauli Exclusion Principle- at most 2 electrons per orbital – having different “spins”
Electron Configuration• Hund’s Rule- When electrons occupy orbitals
of equal energy they don’t pair up until they have to.
[ “don’t want roomate unless it costs more” – more energy in this case]
• Let’s determine the electron configuration for Phosphorus
• Need to account for 15 electrons
• The first 2 electrons go into the 1s orbital
• Notice the opposite “spins”- arrows pointed up then down
• only 13 more e- to go
Incr
easi
ng e
ner
gy
1s
2s
3s
4s
5s
6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
• The next electrons go into the 2s orbital
• only 11 more
Incr
easi
ng e
ner
gy
1s
2s
3s
4s
5s
6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
• The next electrons
go into the 2p orbital
• only 5 more
Incr
easi
ng e
ner
gy
1s
2s
3s
4s
5s
6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
• The next electrons
go into the 3s orbital
• only 3 more
Incr
easi
ng e
ner
gy
1s
2s
3s
4s
5s
6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
Incr
easi
ng e
ner
gy
1s
2s
3s
4s
5s
6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
• The last three electrons go
into the 3p orbitals.
• They each go into separate
shapes
• 3 unpaired electrons
• 1s22s22p63s23p3 is written
electron configuration
Other ways to show this
1s 2s 2p 3s 3p 4s 3d
__ __ __ __ __ __ __ __ __ __ __ __ __ __ __
1s 2s 2p 3s 3p 4s 3d
Other ways to show this
1s 2s 2p 3s 3p 4s 3d
__ __ __ __ __ __ __ __ __ __ __ __ __ __ __
1s 2s 2p 3s 3p 4s 3d
Energy diagrams for Phosphorous atom
The easy way to remember –draw this chart in this way
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
• 1s2
• 2 electrons
Fill from the bottom up following the arrows
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
• 1s2 2s2
• 4 electrons total
Fill from the bottom up following the arrows
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
• 1s2 2s2 2p6 3s2
• 12 electrons total
Fill from the bottom up following the arrows
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
• 1s2 2s2 2p6 3s2
3p6 4s2
• 20 electrons total
Fill from the bottom up following the arrows
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
• 1s2 2s2 2p6 3s2
3p6 4s2 3d10 4p6
5s2
• 38 electrons total
Fill from the bottom up following the arrows
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
• 1s2 2s2 2p6 3s2
3p6 4s2 3d10 4p6
5s2 4d10 5p6 6s2
• 56 electrons total
Fill from the bottom up following the arrows
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
• 1s2 2s2 2p6 3s2
3p6 4s2 3d10 4p6
5s2 4d10 5p6 6s2
4f14 5d10 6p6 7s2
• 88 electrons total
Fill from the bottom up following the arrows
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
• 1s2 2s2 2p6 3s2
3p6 4s2 3d10 4p6
5s2 4d10 5p6 6s2
4f14 5d10 6p6 7s2
5f14 6d10 7p6
• 108 electrons
Exceptions to Electron Configuration
( know that there are exceptions, based upon special circumstances, but don’t memorize or don’t focus on predictions)
Orbitals fill in order • Lowest energy to higher energy.
• But the adding of electrons can change the energy of the orbital.
• Half filled orbitals have a lower energy.
• Makes them more stable.
• Changes the filling order if movement of electrons will allow for half or full fill
Write these electron configurations
• Titanium - 22 electrons
1s22s22p63s23p64s23d2
• Vanadium - 23 electrons 1s22s22p63s23p64s23d3
• Chromium - 24 electrons
1s22s22p63s23p64s23d4 is expected
• But this is wrong!!
Chromium is actually
• 1s22s22p63s23p64s13d5
• Why?
• This gives us two half filled orbitals (4s and 3d).
• The overall configuration has slightly lower energy.
• The same principal applies to copper.
Copper’s electron configuration
• Copper has 29 electrons so we expect
1s22s22p63s23p64s23d9
• But the actual configuration is
1s22s22p63s23p64s13d10
• This gives one filled orbital and one half filled orbital (4s is half, 3d is full); makes for less total energy needs.