unit 1 – atomic structure lesson 1: the electromagnetic spectrum
TRANSCRIPT
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Unit 1 – Atomic StructureLesson 1: The Electromagnetic Spectrum
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Wavelength & Frequency• Wavelength– Measured in nm distance between 2 peaks
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• Frequency• Measured in Hz # of wavelengths passing a given point in
a second
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Electromagnetic Spectrum
• As wavelength decreases, frequency increases
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Types of Radiation• Gamma Rays– Highest frequency– Sources: nuclear reactions,
outer space– Have enough penetrating
ability to pass through 3 meters (9 feet!) of concrete
– In large amounts can cause radiation poisoning
– When controlled, can be used to help cure some cancers
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• X-Rays– Extensively used in the medical field – Uncontrolled exposure to x-rays, can lead to
mutations or cell damage– Used by geologists & chemists for characterizing
the structure & properties of crystalline materials
Types of Radiation
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• UV – Some exposure
promotes Vitamin D production and tanning
– Too much can lead to sunburn, retina damage and cancer
Types of Radiation
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More UV uses
– Kills micro-organisms in water and food– Hardens casts – Insects & birds use UV for navigation
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• Infrared (IR)– Molecules existing above
absolute zero (-273 Celsius) all emit IR, recorded as heat
– ½ of the Sun’s energy is emitted in the IR region
– Tungsten light bulbs are inefficient. They produce more IR than actual visible light
Types of Radiation
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Infrared Cont’d
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Types of Radiation• Microwaves– Highest frequency– Emitted by Earth, buildings, cars, planes– Low level radiation in space
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• Radio waves
Types of Radiation
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Types of Radiation• Visible light (radiation our eyes see)– Ranges from 780 nanometers (deep red) to 400
nanometers (violet)– ROYGBIV– Also called a “continuous spectrum
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Visible light cont’d
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Visible light cont’d• Electrons travel in specific orbits• Emit light when they give off the energy they
acquired & fall back to their original orbit
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Spectroscopy
• Emission– Study of the line spectra given off by electrons
returning to their original energy level• Absorption– Study of the dark lines of a spectra which
represents the energy that was absorbed by a sample
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The Glowing Pickle!
• http://www.youtube.com/watch?v=QZieGLO9_ks
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Historical Development of The Atomic Model
• John Dalton (1766-1844)– English school teacher,
interested in chemistry, physics and meteorology
– Developed atomic theory– Published the first list of
atomic weights– Died in 1844 after suffering
from repeated strokes for over 7 years, although he continued to contribute effectively to science
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Dalton’s Atomic Theory
1. All elements are composed of tiny, indivisible particles called atoms
2. Atoms of the same element are identical and those of different elements are different
3. Atoms of different elements can physically mix together or chemically combine in simple whole number ratios to form compounds
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4. While chemical reactions occur when atoms are separated, joined, or rearranged, atoms of one element are never changed into atoms of another element as a result of a chemical reaction
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JJ Thomson (1856-1940)
• Plum pudding model
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Ernest Rutherford (1871-1937)“gold foil experiment”
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Neils Bohr (1885-1962)
• Proposed electrons are arranged in orbits
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-Electrons cannot exist between energy levels-To move up an energy level an electron must gain enough electricity-When it loses this acquired energy, it moves back down to its original energy level
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Incr
easi
ng e
nerg
y
Energy Levels
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Louis de Broglie (1892-1987)• Wave particle theory• Related circumference of
orbit to whole number wavelengths of an electron travelling around the nucleus
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Erwin Schrodinger (1887-1961
• Defined the probability of finding an electron around the nucleus