Chapter 9.pptx - Chapter 9 Electrons in Atoms and the...

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“Protons give an atom its identity, electrons its personality.” - Bill Bryson, A Short History of Nearly Everything Chapter 9 Electrons in Atoms and the Periodic Table
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Now to start something totally different. Most of us perceive the world around us from reflected light. The old saying is “seeing is believing”. But, what is light? Light is not matter. It has no mass. Electromagnetic Spectrum
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Now to start something totally different. Most of us perceive the world around us from reflected light. The old saying is “seeing is believing”. But, what is light? Light is not matter. It has no mass. Light is a form of electromagnetic radiation a type of energy that travels through space at a constant speed of 3.0 x . Electromagnetic Spectrum
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Light has a dual nature. It can be seen as either a wave or as a particle. The idea that light can act as a wave leads to the idea that these wave will have certain wavelengths ( the distance between adjacent wave crests. Electromagnetic Spectrum
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For visible light, wavelength determines color. Red light, with a wavelength of 750 Nm (nanometers), has the longest wavelength of visible light. Violet light, with a wavelength of 400 nm, has the shortest wavelength of visible light. Visible light is a small portion of the electromagnetic spectrum, which ranges from m (gamma rays) to The shorter the wavelength the greater the energy of the wave. So, gamma rays have the highest energy in the electromagnetic spectrum. Electromagnetic Spectrum
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Electromagnetic Spectrum
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Light waves are also characterized by their frequency (ν) , the number of cycles, or crests that pass through a stationary point in one second. Electromagnetic Spectrum.
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Wavelength and frequency are inversely related – the shorter the wavelength, the higher the frequency. So, high frequency means high energy as well. Early in the twentieth century, light was seen to have the properties of particle. A particle of light is called a photon , and is described as a single packet of light. The energy of the photon is determined wavelength. Think of each wavelength as being a photon. Electromagnetic Spectrum
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Wavelength and frequency are inversely related – the shorter the wavelength, the higher the frequency. So, high frequency means high energy as well. Early in the twentieth century, light was seen to have the properties of particle. A particle of light is called a photon , and is described as a single packet of light. The energy of the photon is determined wavelength. Think of each wavelength as being a photon. That an item can have apparently mutually exclusive properties (such as being a wave or a particle) depending on the experimental framework is called complementarity. Electromagnetic Spectrum
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Niels Bohr, a Danish physicist, developed a theory to describe the internal structure of the atom, in 1912.
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