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Modern Atomic Model and EMR

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Describe the electromagnetic spectrum in terms of frequency, wavelength, and energy. Include: quantum, photon Understand how unique line spectra are created for each element. Additional KEY Terms SpectroscopyEmission Line spectrum

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Maxwell (1860) - all energy radiated from objects (including visible light) is electromagnetic radiation. Composed of radiated waves of both electrical and magnetic energy

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Wavelength and frequency are inversely related Wavelength (λ - “lambda”): distance from point to the same point on the next wave. Frequency (ν – “nu” or ƒ): number of wavelengths, or cycles, that pass a point per unit time. Frequency measured in cycles per second (s -1 ), or the SI unit hertz (Hz) Amplitude: height of the wave from origin to crest. Wavelength and frequency do not affect amplitude

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Types of Electromagnetic radiation f and λ determine what you see or feel, amplitude determines how bright or hot Memorize this wavelength range…

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Sunlight (white light) shone through a prism separates it into a continuous spectrum of colours. The different wavelength for each colour causes them to refract or bend at different angles

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All EMR radiates at 3.00 x 10 8 m/s in a vacuum. This universal value (c) is a product of the wavelength and frequency of the radiated energy. “speed of light” c = λƒ

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The colours seen in fireworks are a result of burning different salts. Red light has a wavelength of 650 nanometres. Calculate the frequency of red light (1 nm - 1.0 x 10 -9 m). ƒλc = ƒ 650 x 10 -9 m = 3.00 x 10 8 m/s ƒ = 4.6 x 10 14 Hz

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ColourElement greencopper yellowsodium redstrontium yellow- green barium orange-redcalcium purplepotassium purple-redlithium Burning small amounts of each element gave off a unique colour of light Used to detect a metals presence Planck (1900) Focusing this light through a prism also produces a spectrum, but ONLY distinct lines appear Investigated heating objects and

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Energy emitted by a element can be separated – to produce a Line spectrum (emission spectrum) Disclaimer: This is not as simple as my “art” looks

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The colored lines of the atoms (or Spectral Lines) are a kind of "signature" for the atoms. C O Spectroscopy and spectrophotometry are techniques used to investigated EMR emissions.

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Planck's Radiation Law: Energy is transmitted in discrete amounts – called quanta. EMR is a stream of tiny “packets” of quantized energy carried by particle-like photons. A photon has no mass but carries a quantum of energy

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E q = hf E – energy of a quantum (Joules) h – Plank’s constant (6.626 x 10 -34 J s) f – frequency of absorbed or emitted EMR Energy (quantum) contained in a photon is directly related to the frequency of the radiation. So higher frequency waves contained larger “packets” of energy

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The blue colour of fireworks is often achieved by heating copper (I) chloride to about 1200 o C. The wavelength of the blue light is 450 nm. What is the quantum of energy emitted by this light? E = hf ƒ = c λ ƒ 450 x 10 -9 m = 3.00 x 10 8 m/s ƒ = 6.7 x 10 14 Hz E = (6.626 x 10 -34 J · s)(6.7 x 10 14 Hz) E = 4.4 x 10 -19 J q

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CAN YOU / HAVE YOU? Describe the electromagnetic spectrum in terms of frequency, wavelength, and energy. Include: quantum, photon Understand how unique line spectra are created for each element. Additional KEY Terms SpectroscopyEmission Line spectrum

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