Electron Electron ConfigurationConfiguration

3.33.3

ModelsModels

• 1st model of the atom– Rutherford “plum pudding”

• Next model– Bohr, 2 years later

– Introduced the idea of energy levels• The difference between 2 energy levels is a quantum of energy.

Present ModelPresent Model

• Orbitals are like clouds.– Show areas where electrons are likely to be

found.• Like the propellers on an airplane or helicopter.

Light is a Wave…Light is a Wave…

• Light travels in waves.• 2.998 x 108 m/s

• ROYGBIV

• Different colors have different energies.– Blue end is more energetic than the red end of

the spectrum.

Light is a particle?Light is a particle?

• Einstein said light is a particle.– Observed the photoelectric effect.

• When light strikes metal, electrons are released.– This only happens at certain frequencies.

Light EmissionLight Emission

• When energy is absorbed, electrons can move from a lower energy level to a higher energy level.

• Electrons cannot maintain the higher state and fall back to their lower level. When this happens they release the energy they absorbed.– Produces light.

StateState

• Ground State– State of lowest possible energy

– Where e- normally are

• Excited State– Where e- moves when energy is absorbed

– Can’t stay…

– Emits light when falls back to ground state

Energy LevelsEnergy Levels

• s– Can contain only 2 e-

• p– Can contain 6 e-

• d– Can contain 10 e-

• f– Can contain 14 e-

Aufbau PrincipleAufbau Principle

• The aufbau (German for “building up”) principle tells us the order to follow when writing energy levels and the e- they contain.

• The next slide is extremely important.

Aufbau PrincipleAufbau Principle

1s2

2s2 2p6

3s2 3p6 3d10

4s2 4p6 4d10 4f14

5s2 5p6 5d10 5f14

6s2 6p6 6d10 6f14

7s2 7p6 7d10 7f14

PracticePractice

Write electron orbital configurations for the elements below:

5 e- 27 e-18 e-19 e- 23 e-

Stop and go to doc-cam

AnswersAnswers

B 1s22s22p1

Co 1s22s22p63s23p64s23d7

Ar 1s22s22p63s23p6

K 1s22s22p63s23p64s1

V 1s22s22p63s23p64s23d3

Electrons & the Periodic Electrons & the Periodic TableTable

• The periodic table is arranged by increasing atomic number (# of p+).

• Each element is 1 proton and electron higher than the one before it.

• It is an acceptable shortcut to write the electron configuration for larger elements by noting the symbol of the noble gas on the previous line before it followed by the remaining orbitals.

• ???

ExamplesExamples

• Oxygen 1s22s22p4

can be written as [He] 2s22p4

• Br 1s22s22p63s23p64s23d104p5

can be written as [Ar] 4s23d104p5

1s2

2s2 2p6

3s2 3p6 3d10

4s2 4p6 4d10 4f14

5s2 5p6 5d10 5f14

6s2 6p6 6d10 6f14

7s2 7p6 7d10 7f14