Chemistry Quantum Atomic Theory Part 2 PDF

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This document is a chemistry textbook excerpt on Quantum Atomic Theory Part 2. It explains the concepts of energy levels and sublevels, introducing quantum numbers and orbitals. The document provides useful information for chemistry students learning quantum atomic theory.

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1 Energy Levels and Sublevels In atoms electrons occupy energy sublevels within each level. These sublevels are given the designations s, p, d, and f. These designations are about the sharp, principal, diffuse, and fine lines in emission spectra. The number of sublevels in each le...

1 Energy Levels and Sublevels In atoms electrons occupy energy sublevels within each level. These sublevels are given the designations s, p, d, and f. These designations are about the sharp, principal, diffuse, and fine lines in emission spectra. The number of sublevels in each level is the same as the number of the main energy level. Think of the energy level as a floor in a building, and sublevels as separate apartment units on each floor. Copyright © 2023 Pearson Canada Inc. 7-1 Principal Quantum Number (n) - informs about the energy level of the orbital - how far the orbital is from the nucleus - size of the orbital - the “floor” of the apartment  1  En = −2.18  10−18 J  2  n  n = 1, 2, 3K 7.14 Copyright © 2023 Pearson Canada Inc. 7-2 Angular Momentum Quantum Number (l) - informs about the type of orbital (s, p, d or f) - each orbital has an assigned value of l - specific apartment unit on each floor in the building l = 1, 2, 3, , n − 1 Value of l Letter Designation l=0 s l=1 p l=2 d l=3 f Copyright © 2023 Pearson Canada Inc. 7-3 Magnetic Quantum Number (ml) - informs about how many possible orientations in space an orbital can have ml = −l to + l Copyright © 2023 Pearson Canada Inc. 7-4 s Orbitals (1 of 3) s Orbitals (l = 0) - what is the n number for 1s orbital? - how many ml numbers can s orbital have? - therefore, how many possible orientations in space can an s orbital have? Figure 7.26 The 1s Orbital Surface Copyright © 2023 Pearson Canada Inc. 7-5 p Orbitals (l = 1) - what is the n number for 3p orbital? - how many ml numbers can p orbital have? - therefore, how many possible orientations in space can an p orbital have? Figure 7.29 (a) The 2p Orbitals Copyright © 2023 Pearson Canada Inc. 7-6 d Orbitals (l = 2) - what is the n number for 5d orbital? - how many ml numbers can d orbital have? - therefore, how many possible orientations in space can a d orbital have? Figure 7.30 The 3d Orbitals Copyright © 2023 Pearson Canada Inc. 7-7 d Orbitals Sketching You need to know how to sketch and annotate s, p, and d orbitals. Always start with setting up the system of coordinates Draw and mark the lobes, nodes and write down which one of the p or d orbitals you drew (subscript notation e.g. px, py, pz) Copyright © 2023 Pearson Canada Inc. 7-8 f Orbitals (l = 3) - how many ml numbers can f orbital have? - therefore, how many possible orientations in space can f orbital have? - what is the orbital with the following quantum numbers: n=5 l=1 - how many orientations in space can it have? name them Figure 7.31 The 4f Orbitals Copyright © 2023 Pearson Canada Inc. 7-9 The Phase of Orbitals Copyright © 2023 Pearson Canada Inc. 7 - 10 7.7 Electron Configurations: How Electrons Occupy Orbitals Electron Spin and the Pauli Exclusion Principle Copyright © 2023 Pearson Canada Inc. 7 - 11 The Pauli Exclusion Principle Pauli Exclusion Principle: No two electrons in an atom can have the same four quantum numbers n l ml ms or two electrons in the same orbital 1 0 0 +1/2 (box) have to point in the opposite 1 0 0 −1/2 directions Copyright © 2023 Pearson Canada Inc. 7 - 12 Electron Configurations for Multielectron Atoms (1 of 3) - get the total number of electrons to distribute from the periodic table (that will be the sum of all superscripts in the electron configuration) - get the number of energy levels n (from the period) 1. First electrons fill the energy sublevel closest to the nucleus. 2. Electrons continue filling each sublevel until it is full, and then start filling the next closest sublevel. The maximum number of electrons in each of the energy sublevels depends on the sublevel: The s sublevel holds a maximum of 2 electrons. The p sublevel holds a maximum of 6 electrons. The d sublevel holds a maximum of 10 electrons. The f sublevel holds a maximum of 14 electrons. Copyright © 2023 Pearson Canada Inc. 7 - 13 Copyright © 2023 Pearson Canada Inc. 7 - 14 Suborbital Filling Order Electrons start filling orbitals from the lowest energy and up (Aufbau principle) Note the order is not exactly as one would predict as there are some regular deviations, e.g. 4s has lower energy than 3d For now use the diagram to predict order of sublevel filling Copyright © 2023 Pearson Canada Inc. 7 - 15 Electron Configurations for Multielectron Atoms (2 of 3) Hund’s rule - electrons will fill orbitals individually before pairing up in one orbital. Copyright © 2023 Pearson Canada Inc. 7 - 16 Electron Configurations for Multielectron Atoms (3 of 3) Copyright © 2023 Pearson Canada Inc. 7 - 17 Electron Configurations for Transition Metals (1 of 3) 4s and 3d orbitals are very close in energy, and for K and Ca the 4s is lower in energy than the 3d. Relative orbital energies vary due to nuclear charge and electron filling resulting in variations of relative 4s and 3d energies. This becomes obvious in the electron filling of transition metal orbitals. Copyright © 2023 Pearson Canada Inc. 7 - 18 Electron Configurations for Transition Metals (2 of 3) The relative energies of the 3d, 4s, 4d, and 5s orbitals of the free neutral atoms with atomic numbers 1-46 [Data from Wang, S. G.; Qiu, Y. X.; Fang, H.; Schwarz, W. H. The challenge of the so-called electron configurations of the transition metals. Chem. Eur. J. 2006, 12, 4101–14]. Copyright © 2023 Pearson Canada Inc. 7 - 19 Electron Configurations for Transition Metals (3 of 3) TABLE 7.3 First-Row Transition Metal Orbital Occupancy Copyright © 2023 Pearson Canada Inc. 7 - 20 Electron Configurations and Magnetic Properties of Ions (1 of 2) When writing the electron configuration of a transition metal cation, remove the electrons in the highest n-value orbitals first, even if this does not correspond to the reverse order of filling. Copyright © 2023 Pearson Canada Inc. 7 - 21 Electron Configurations and Magnetic Properties of Ions (2 of 2) Paramagnetic: unpaired electrons generate a magnetic field and are attracted to an external magnetic field Diamagnetic: paired electrons do not generate a magnetic field and are slightly repelled by an external magnetic field. Copyright © 2023 Pearson Canada Inc. 7 - 22

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