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Homework

Homework. Read pages 360 – 364 372 – 375 379 & 380. Electrons in The atom. Further developments in the models of the atom. Nature Of Light (background Info). Electromagnetic radiation Def : form of energy that exhibits wave and particle behavior while traveling through space.

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Homework

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  1. Homework Read pages 360 – 364 372 – 375 379 & 380

  2. Electrons in The atom Further developments in the models of the atom

  3. Nature Of Light(background Info) Electromagnetic radiation Def: form of energy that exhibits wave and particle behavior while traveling through space

  4. Wave Characteristics 1. wavelength(l) – distance between corresponding points on consecutive waves 2. frequency(n) – the number of waves that pass through a point in a given amt of time (Hz) 3. Amplitude - the maximum displacement from rest

  5. Wave Speed • Speed = l n 2. EM radiation travels at constant speed in a vacuum: c = 3.0 x 108 m/s or 186,000 miles/s 3. Speed is constant for EM waves, therefore, frequency is inversely proportional to wavelength

  6. Frequency vs wavelength

  7. EM Spectrum • consists of all electromagnetic radiation, arranged according to wavelengths

  8. EM Waves and Energy • The energy carried by an EM wave can be determined using the following equation: Energy = Planck’s constant x frequency OR E = h f where E = energy in Joules h = 6.63 x 10 -34 J s f = frequency in Hz - Energy of the wave is directly proportional to the frequency of that light wave

  9. Light from Elements

  10. Bohr Model of the Atom • The chemical behavior of atoms depends on the arrangement of their electrons • Electrons orbit the nucleus in concentric circular paths • He proposed that the reason the electrons ( negatively charged particles) do not fall into the nucleus (positively charged) is because electrons orbit the nucleus with specific fixed amounts of energy

  11. Bohr Model of the Atom Each energy level is associated with a specific amt of energy (called Principle Energy Levels or PEL) Further from nucleus, greater the energy of an electron Max # electrons in a PEL = 2n2

  12. Bohr Model (cont’d)Why do atoms give off light? animation Electrons occupy the lowest possible energy level (ground state) If they absorb sufficient energy, they make a quantum leap to higher energy level (excited state)

  13. Emission Spectra Excited electrons are unstable and will fall to ground state Give off a burst of energy called a quantum of energy A quantum of energy that falls in visible spectrum called Photon

  14. Electron Configurations(Bohr Model) Shows the arrangement of electrons in an atom Each element on your Periodic Table has an electron configuration Indicates the number of electrons in each energy level for that atom

  15. Write the electron configuration for an atom of sodium, Na, on the line below. __________________________________ How many electrons occupy the 1st PEL ? _________ How many electrons occupy the 3rd PEL? _________ Write a possible electron configuration for an exited atom of sodium. _______________________________

  16. Quantum Mechanical Model of Atom Modern model of the atom

  17. What was so wrong with the Bohr model of the atom? The Bad • could not predict spectra for atoms with more than one electron • Heisenberg Uncertainty Principle – the location of an electron cannot be known at any one point in time The Good accurately predicted emission spectra of hydrogen

  18. How did it change? • Electrons were found to have wave – like properties • Scientists began to treat electrons as waves and particles at the same time, developing new ideas on what an atom “looks” like as a result of these properties

  19. Quantum Mechanical Model Electrons are found in areas of definite energy (PELs) Electrons do not travel in definite paths around nucleus

  20. Where are the electrons? Electrons are located in areas of most probable location (orbitals) Visualized as a cloudy like region around the nucleus

  21. Orbitals Electrons found in orbitals which are part of a sublevel of each energy level

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