3.3 electron configuration
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The document discusses electron configuration and energy levels. It introduces the historical models of the atom including Rutherford's plum pudding model and Bohr's model introducing energy levels. Modern models use orbitals that show the probability of finding electrons. Light can be described as both a wave and particle. Electrons absorb energy to move to excited states then emit light returning to ground states. Elements' electron configurations follow the aufbau principle filling lower energy orbitals first up to the periodic table.
![ExamplesExamples
• Oxygen 1s2
2s2
2p4
can be written as [He] 2s2
2p4
• Br 1s2
2s2
2p6
3s2
3p6
4s2
3d10
4p5
can be written as [Ar] 4s2
3d10
4p5](https://image.slidesharecdn.com/3-131006090315-phpapp02/85/3-3-electron-configuration-14-320.jpg)
3.3 electron configuration
- 2. 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.
- 3. Present ModelPresent Model • Orbitals are like clouds. – Show areas where electrons are likely to be found. • Like the propellers on an airplane or helicopter.
- 4. 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.
- 5. 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.
- 6. 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.
- 7. 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
- 8. Energy LevelsEnergy Levels • s – Can contain only 2 e- • p – Can contain 6 e- • d – Can contain 10 e- • f – Can contain 14 e-
- 9. 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.
- 11. 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
- 12. AnswersAnswers B 1s2 2s2 2p1 Co 1s2 2s2 2p6 3s2 3p6 4s2 3d7 Ar 1s2 2s2 2p6 3s2 3p6 K 1s2 2s2 2p6 3s2 3p6 4s1 V 1s2 2s2 2p6 3s2 3p6 4s2 3d3
- 13. Electrons & the Periodic TableElectrons & the Periodic Table • 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. • ???
- 14. ExamplesExamples • Oxygen 1s2 2s2 2p4 can be written as [He] 2s2 2p4 • Br 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 can be written as [Ar] 4s2 3d10 4p5