• 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

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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

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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

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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

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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

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1s

2s

3s

4s

5s

6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

Incr

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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.