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Clicker #1 How many of the following statements are true? I. All atoms of the same element are identical. II. Negatively charged particles are embedded in a positively charged cloud throughout the atom. III. As verified by Rutherford, only positively charged particles called protons are found inside the nucleus. IV. J.J. Thomson provided the first experimental support for the atom. A) 0 B) 1 C) 2 D) 3 E) 4
White Light • Why is white light white? • Energy: • Related to the wavelength of light (also relates to the colors of light) • Travels through space (Electromagnetic Radiation- contains visible light)
Electromagnetic Spectrum Increasing Wavelength Increasing Energy http://en.wikipedia.org/wiki/File:EM_Spectrum_Properties_edit.svg
Example: Light Bulb Energy as Light and Heat Heating Wire (resistance through a wire)
Clicker #2 Why does the pickle (the system) give off light? Choose the best answer. A) If you run electricity through anything, it will give off light. B) When protons are in an excited state due to electricity, they glow. C) The pickle contains sodium. The electricity is causing the neutrons inside sodium to move across between the two forks and thus make it glow. D) Energy was put into the pickle (by electricity) so it’s returning back to a lower energy state by releasing light.
What puts atoms in an excited state? • Applied Energy! • Electrons MOVE AROUND • Electrons • Like to be near nucleus • Need energy forces to keep them away • Energy released when electrons fall back toward nucleus Colored light!!!
Energy Levels • Only certain energy levels are allowed • DEMO: Flame Tests • Different colors = Different Ions • NONE are white light • ENERGY is NOT a continuous spectrum • ENERGY is DISCRETE spectrum
“Quantized” Energy Levels • Time travel ..VERSUS.. • Quantum Leap
“Quantized” Energy Levels • Energy emitted/absorbed from an atom in discrete packets • Electrons excited or released toward ground state to specific energy levels
Niels Bohr Model http://abyss.uoregon.edu/~js/cosmo/lectures/lec08.html
Niels Bohr Model WRONG!!!! http://abyss.uoregon.edu/~js/cosmo/lectures/lec08.html
Niels Bohr Model • Good at explaining energy levels • Electrons go from one energy level to another • Electrons can ONLY exist at certain energy levels • Works well mathematically for Hydrogen, but not for other elements http://abyss.uoregon.edu/~js/cosmo/lectures/lec08.html
Clicker #3 When an electron is excited in an atom or ion A) the electron moves further from the nucleus. B) only specific quantities of energy are released in order for the electron to return to its ground state. C) white light is never observed when the electron returns to its ground state. D) the electron is only excited to certain energy levels. E) All of the above statements are true when an electron is excited.
“Waves” and “Particles” • An electron can behave like a particle • An electron can behaves like a wave • (every electron has a wavelength associated with it) • Louis Victor de Broglie and Erwin Schrödinger
Wave Properties • Can cancel and add up • The more energy they have the more complicated the wave gets • Waves are associated with probability • If a wave cancels (i.e.- wavelength = 0) then there is zero probability you will find an electron there • QUANTIZED ENERGY!!!!!!!!
Think of electrons in terms of probabilities! • Firefly example