Download - Chapter 4 Electron Configurations
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Chapter 4 Electron Configurations
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Early thoughtsMuch understanding of electron behavior comes from studies of how light interacts with matter.Early belief was that light traveled as a wave, but some experiments showed behavior to be as a stream of tiny fast moving particles
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Waves Today scientists recognize light has properties of waves and particlesWaves: light is electromagnetic radiation and travels in electromagnetic waves.
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4 Characteristics of a wave:1) amplitude - height of the wave. For light it is the brightness2) Wavelength () distance from crest to crest. For light defines the type of light Visible light range 400-750nm
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Properties continued3) Frequency () measures how fast the wave oscillates up and down. It is measured in number per second. Hertz = 1 cycle per secondFM radio = 93.1 MHz or 93.1 x 106 cycles per secondVisible light = 4 x 1014 cycles per second to 7 x 1014 cycles per second 4) speed 3.00 x 108 m/s
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Short wavelength, high frequencyLong wavelength, low frequencyVisible SpectrumROY G BIV Longer wavelength shorter wavelength
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Electromagnetic spectrum (meters)10-11 gamma10-9 x-rays10-8 UV10-7 visible light10-6 infrared10-2 microwave1 TV
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Wavelength and frequencyWavelength and frequency are inversely related!! = c/Where is the wavelength, c is the speed of light and is the frequencySpeed of light = Constant = 3.00 x 108m/sec
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ExampleExample: An infrared light has a wavelength of 2.42 x 10-6m. Calculate the frequency of this light. = c/ = 3.0 x 108m/sec = 2.42 x 10-6m= 1.2 x 1014 waves/sec
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Wavelength and frequency****Remember and are inverse. Therefore short wavelength = high frequency!!
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Quantum TheoryNeeded to explain why certain elements when heated give off a characteristic light (certain color)1900- Max Planck idea of quantum
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Quantum Theory- The amount of energy (electromagnetic radiation) an object absorbs/emits occurs only in fixed amounts called quanta (quantum)- Quanta finite amount of energy that can be gained or lost by an atom.
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1905 Einsteins theoryEinstein explained photoelectric effect by proposing that light consists of quanta of energy called PHOTONS Photon = discrete bit of energy Consider light traveling as photons
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Energy equationAmount of energy of a photon described asE = hWhere E = energy = frequencyh = Plancks constant = 6.6262 x 10-34 J sJoule = SI unit for energy
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Photoelectric effect electrons are ejected from the surface of a metal when light shines on the metal. The frequency determines the amount of energy. The higher the frequency, the more energy per photon.
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Photoelectric effectEx. X-rays have a high frequency; therefore can damage organisms while radio waves have a low frequency.
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Dual nature of radiant energy Photons act both like particles and waves.Line Spectra: A spectrum that contains only certain colors, or wavelengths
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Question: How are electrons arranged in atoms?
Note: All elements emit light when they are vaporized in an intense flame or when electricity is passed through their gaseous state.
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How are electrons arranged in atoms?Explanation: Bohr atom: 1911postulated that atoms have energy levels in which the electrons orbitenergy levels and/or orbits are labeled by a quantum number, n. lowest energy level = ground state n=1
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How are electrons arranged in atoms?when an electron absorbs energy, it jumps to a higher level (known as the excited state) n = 2,3 or 4Bohr model of an atom Hydrogen Red- e falls from 3 to 2Blue e falls from 4 to 2Violet e falls from 6 to 2
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1924 Louis DeBroglie If waves of light can act as a particle, then particles of matter should act like a wave. Found to be true.
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DeBroglieMatter waves = wavelike behavior of particles.From equation wave nature is inversely related to mass therefore we dont notice wave nature of large objects. However, electrons have a small mass so they have a larger wave characteristic
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Schroedingers wave equationpredicted probability of finding an electron in the electron cloud around nucleus. Gave us four quantum numbers to describe the position.
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Heisenbergs Uncertainty PrincipleThe position and momentum of a moving object cannot simultaneously be measured and known exactly.Cannot know where it is and where its going at the same time.
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Quantum mechanical model of an atom Treats the electrons as a wave that has quantized its energyDescribes the probability that electrons will be found in certain locations around the nucleus.
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OrbitalsOrbitals atomic orbital is a region around the nucleus of an atom where an electron with a given energy is likely to be found (high probability)Have characteristic shapes, sizes and energies.Four different kinds of orbitals s, p, d, f.
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S and p orbitals
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Orbitals and energy
Principal Energy Level = quantum number n. Principal Quantum number Value of n = 1,2,3,4,5,6,7Tells you the distance from the nucleus
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sublevelsEach level is divided into sublevels# of sublevels = value of nN=1 1 subleveln=2 2 sublevels s,p,d or f shows the shape
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Orbital shapeEach sublevel has a certain number of orbitals which are directed three dimensionally S = 1 sphereP = 3 figure 8 (along the x,y or z axis)D = 5 figure 4-27 p. 145F = 7
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Each electron in an orbital will have a spin 2 options clockwise, vs. counter clockwise.Electron configurationPauli Exclusion Principle each orbital in an atom can hold at most 2 electrons and their electrons must have opposite spin.
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Aufbau Principle- electrons are added one at a time to the lowest energy orbitals availableHunds Rule electrons occupy equal energy orbitals so that the maximum number or unpaired electrons result. Occupy singly before pairing
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Diagonal Rule: for order of sublevels: must remember 1s, 2s, 2p, 3s, 3p, 4sExceptions to Aufbau PrincipleCr Z=24 Cu Z = 29
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Energy levelsNumber of electrons per energy level1st = 22nd = 83rd = 184th = 32
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Number of electrons per orbital2Difference between paired and unpaired electronsPaired = 2 electrons in the same orbitalUnpaired = 1 electron in the orbital