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Chapter 5

Chapter 5. Electrons in Atoms. 5.1 Light and Quantized Energy. Rutherford’s atomic model – nucleus surrounded by fast-moving electrons- not complete model. Rutherford’s model did not explain why certain elements behave the way they did Certain elements emitted light when heated.

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Chapter 5

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  1. Chapter 5 Electrons in Atoms

  2. 5.1 Light and Quantized Energy • Rutherford’s atomic model – nucleus surrounded by fast-moving electrons- not complete model

  3. Rutherford’s model did not explain why certain elements behave the way they did • Certain elements emitted light when heated

  4. Light can behave as a wave and a particle!

  5. Wave Nature of Light • Electromagnetic Radiation-form of energy that exhibits wavelike behavior • Ex: visible light, microwaves, x-rays

  6. Electromagnetic Spectrum-encompasses all forms of EM radiation

  7. Electromagnetic Spectrum

  8. The WAVE!

  9. Wavelength (λ )-shortest distance between equivalent points on a continuous wave • Measured crest to crest or trough to trough

  10. Frequency (f )-number of waves that pass a given point per second • 1 Hertz (Hz) = 1 wave per second • SI unit of frequency • Amplitude-wave’s height from the origin to a crest or from origin to trough

  11. Speed of light = frequency x wavelengthC = fλ • C = 3.0 x 108 m/s • as wavelength increases, frequency decreases & vice versa (inversely related)

  12. Sunlight (white light) contains continuous range of wavelengths and frequencies of visible light

  13. Atomic Emission Spectrum-set of frequencies of the EM waves emitted by atoms of the element • Unique to each element, used for identification

  14. Particle Nature of Light • Quantum-minimum amount of energy that can be gained or lost by an atom

  15. Quantum= hf • E = energy • h = Planck’s constant; 6.626 x 10-34 J•s • f = frequency • J is joule; SI unit for energy

  16. Photon-particle of EM radiation with no mass that carries a quantum of energy • Ephoton = hf

  17. WHEN LIGHT BEHAVES LIKE A PARTICLE!

  18. 5.2 Quantum Theory and the Atom • Bohr Model of the Atom- proposed that hydrogen atom has only certain allowable energy states

  19. Ground State-lowest allowable energy state of an atom • Excited State- when an atom gains energy

  20. The lower the energy level, the smaller the orbit • The higher the energy level, the larger the orbit

  21. Orbital - A three-dimensional region around the nucleus of an atom that describes an electron’s probable location

  22. S-Orbital • Spherical in shape

  23. P-Orbital • Dumbbell shaped

  24. 5.3 Electron Configurations • Electron Configuration-the arrangement of electrons in an atom • Electrons tend to assume arrangement to have lowest possible energy

  25. Remember!!! Number of electrons is equal to number or protons, which is equal to the atomic number!!! • Ex: Carbon is atomic number 6, so it has 6 total electrons!

  26. Electron configurationnotation- describes the principal energy level and energy sublevel associated with each of the atom’s orbitals and includes a superscript representing the number of electrons in the orbital

  27. Electron Configuration Examples: O 1s2 2s2 2p4 Cl 1s2 2s2 2p6 3s2 3p5 Al 1s2 2s2 2p6 3s2 3p1

  28. Electron Notation using Noble Gas Notation: O [He] 2s2 2p4 Cl [Ne] 3s2 3p5 Al [Ne] 3s2 3p1

  29. Valence Electrons-electrons in the atom’s outermost orbitals- generally those associated with the atom’s highest principal energy level

  30. Electron-Dot Structure-consists of the element’s symbol (represents nucleus & inner electrons) surrounded by dots representing the atom’s valence electrons • Also known as Lewis Structure

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