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Unformatted text preview: 81Chapter 8Chapter 8Electron Configuration and Electron Configuration and Chemical Periodicity IChemical Periodicity I82A: mass number; A = Z + NZ: atomic number = number of protons in nucleusdetermines the chemical identity of an elementN: number of neutrons in the nucleuse: number of electrons = number of protonsWhere are all the electrons?AZXThe Symbol of the Atom or IsotopeAtomic Symbols, Isotopes, Numbers (Chpt. 2)83Structure of the Atom (Chpt 2)Structure of the Atom (Chpt 2)•Atom the basic structural unit of an element.–The smallest unit of an element that retains the chemical properties of that element84Atomic Theory: the Bohr AtomAtomic Theory: the Bohr AtomElectrons exist in specific energy levels around the nucleus: “Quantization”of energyAbsorption of energy brings the electron to a higher energy level: “promotion” of electron “Excited State”Energy is released as the electron falls back to lower energy levels:“Relaxation”Initial understanding of the H atom by Niels Bohr (18851962)85•Bohr postulated fixed energy levels: “Orbits”•Ground state the lowest possible energy state•Excited state– higher energy level∆E = EC– EB= Ephoton= “quantum” of light 86•The orbits are also identified using “quantum numbers”–n = 1, 2, 3, …n=1n=2n=3•When the electron relaxes (c), the energy released is observed as a single wavelength of light, resulting in a spectral line87Quantum StaircaseQuantum StaircaseElectron Transition in the Hydrogen Emission SpectrumLine colorWavelength (nm)Electron transition fromn =to n =Red656.432Green486.342Blue434.252Violet410.36288The Line Spectra Of Several ElementsThe Line Spectra Of Several Elements89Quantum MechanicsQuantum MechanicsHeisenberg’s Uncertainty Principle•“It is impossible to know the exact location and momentum (= mass x speed) of a particle simultaneously”Erwin Schrödinger•developed mathematical equations that describe the particle and wave nature of electrons •an atom has certain allowed quantities of energy due to the wavelike behavior of an electron whose exact location cannot be knownSchrödinger Equations:•determine the probability of finding an electron in a specific regionin space•define principle energy levels(n = 1, 2, 3…) (Bohr model) •propose sublevelsor subshells(s, p, d, f) and •describe orbital: the specific region with a high probability to find an electron810Modern Atomic TheoryModern Atomic Theory•Revisions of Bohr’s model postulate:–Electrons do notmove in orbits: there are no “orbits” (= fixed energy levels)–There are “atomic orbitals” •regions in space with a high probabilityof finding an electron....
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This note was uploaded on 04/13/2008 for the course CHEM 1311 taught by Professor Baishakhidas,ms. during the Spring '08 term at Alamo Colleges.
 Spring '08
 BaishakhiDas,MS.
 Atomic Number, Electron, Nucleus, Proton, Isotopes

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