CHEM 101 1nd Edition Lecture 27Outline of Last Lecture I. Quantum MechanicsII. Quantum NumbersIII. Common Misconceptions about Orbital ShapesIV. Types of Atomic OrbitalsOutline of Current Lecture I. Electron SpinII. Quantum NumbersIII. Orbital EnergiesIV. Effective Nuclear Charge Z*V. Orbital DiagramsVI. The Periodic TableCurrent LectureI. Electron Spina. Electrons behave as tiny spheres rotating on an axis.b. As a spinning charge they produce a magnetic field.c. Electron spin Is quantized.d. Spin Magnetic Quantum Number msi. Describes the electron spinii. ms = +1/2, -1/2II. Quantum Numbersa. Four quantum numbers n, l, ml, and ms are required to describe an electronb. Up to two electrons can occupy one atomic orbital. When a orbital is doubly occupied the electrons have opposite spinsc. Pauli Exclusion Principlei. No two electron can have the same 4 quantum numbersii. OR no two atomic orbitals can be assigned more than 2 electrons.d. Table 7.1 in Booki. Useful table for orbitals and quantum numbers that can be referred tooIII. Orbital Energiesa. Electrons assigned to subshells with increasing “n + l” valueb. For two subshells with the same “n + l”, electrons are assigned first to the These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.subshell of lower nIV. Effective Nuclear Charge Z*a. Effective nuclear charge: net charge experienced by a particular electron in a multi electron atom resulting from the nucleus and the other electronsi. Lithium has 3 protons in the nucleus, two 1s electrons in the first shell, and 1 2s electron in the second shellii. The 1s orbital screen/shield the 2 s electron from experiencing the full nuclear charge1. Electron repel each otheriii. At large distances the 2s electron will experience a +1 chargeiv. At distances near the nucleus, the 1s electrons do not effectively screen the electron density and the 2s experience a charge of 3+b. The extent at which an outer electron penetrates inner orbitals occurs in the orders s > p > d > fc. Effective nuclear charge experienced by an electron in a multi electron atom is then in the order ns > np > nd > nfi. As a consequence, in a given shell the s electron will have lower energy that p electrons1. Orbital energies: ns < np < nd < nfV. Orbital Diagramsa. Hund’s Rulei. For degenerate orbitals, the lowest energy lis attained when the number of electrons with the same spin in maximizedii. Half-filled orbitals are more stableiii.b. Condensed ElectronConfigurationsi.Element Total Electrons Orbitals e- Configuration CondensedLi 3 Above 1s22s1[He]2s1Na 11 Above 1s22s22p63s1[Ne]3s1c. Valence Electronsi. Valence Electrons: electrons in the outermost (n) orbitalsVI. The Periodic Tablea. If you follow the Periodic Table in order of increasing atomic number, it predicts the order in which the orbitals fill with electrons, so you don’t have to memorize them.b. Exceptions to this will be talks about next time . 1s 2s 2pH ^ ^ = positive electronHe ^v v = negative electronLi ^v ^Be ^v ^vB ^v ^v ^C ^v ^v ^ ^N ^v ^v ^ ^ ^O ^v ^v ^v ^ ^F ^v ^v ^v ^v ^Ne ^v ^v ^v ^v
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