Copyright © 2001 by Harcourt, Inc. All rights reserved. 6.1 Chapter 6 Electronic Structure and the Periodic Table Copyright © 2001 by Harcourt, Inc. All rights reserved. Requests for permission to make copies of any part of the work should be mailed to the following address: Permissions Department, Harcourt, Inc Sea Harbor Drive, Orlando, Florida

Copyright © 2001 by Harcourt, Inc. All rights reserved. 6.2 Characteristics of a wave

Copyright © 2001 by Harcourt, Inc. All rights reserved. 6.3 The electromagnetic spectrum

Copyright © 2001 by Harcourt, Inc. All rights reserved. 6.4 Atomic Spectra Produced when electron moves from higher to lower energy level, giving off light in the process.  E = E hi - E lo = h = hc /

Copyright © 2001 by Harcourt, Inc. All rights reserved. 6.5 Emission spectra

Copyright © 2001 by Harcourt, Inc. All rights reserved. 6.6 Atomic Spectra For the yellow line in the sodium spectrum, = nm ===  /s  E ==  J c  10 8 m/s  m (6.626  J  s)(2.998  10 8 m/s)  m

Copyright © 2001 by Harcourt, Inc. All rights reserved. 6.7 Atomic Spectra For one mole of electrons:  E =  J  = kJ Hence, two energy levels in the Na atom differ in energy by kJ/mol  mol 1 kJ 10 3 J

Copyright © 2001 by Harcourt, Inc. All rights reserved. 6.8 Hydrogen Atom Bohr model : H atom consists of a central proton about which an e - moves in a circular orbit Quantum mechanical model : will-defined orbit at a fixed distance from the nucleus abandoned

Copyright © 2001 by Harcourt, Inc. All rights reserved. 6.9 Bohr model Bohr postulated that an electron moves about nucleus in a circular orbit of fixed radius. By absorbing energy, it moves to a higher orbit of larger energy and energy is given off as the electron returns. E n = n = 1,2,  J n 2

Copyright © 2001 by Harcourt, Inc. All rights reserved Bohr model (cont.) When an electron moves from n = 3 to n = 2: E 3 =  J ; E 2 =  J E hi - E lo =  J = = 6.56  m = nm (1 st line in Balmer series) (6.626  J  s)(2.998  10 8 m/s  J hc  E

Copyright © 2001 by Harcourt, Inc. All rights reserved Quantum mechanical model  Can only refer to the probability of finding an electron in a region; cannot specify path.  The kinetic energy of the electron in an atom is inversely related to volume.  Four quantum numbers are required to describe completely the energy of an electron in an atom.

Copyright © 2001 by Harcourt, Inc. All rights reserved Probability of finding the hydrogen electron in its ground state

Copyright © 2001 by Harcourt, Inc. All rights reserved Electronic Structure of Atoms Principal Energy Levels : the energy depends upon only n Sublevels : general shape of the electron cloud associated with an electron is determined by

Copyright © 2001 by Harcourt, Inc. All rights reserved Principal Energy Levels n = 1,2,3... Value of n is the main factor that determines the energy of an electron and its distance from the nucleus. Maximum capacity of principal level = 2n 2 n Max no. of e

Copyright © 2001 by Harcourt, Inc. All rights reserved Sublevels Quantum number = 0, 1, 2...(n-1) n=1 = 0 (one sublevel) n=2 = 0, 1 (two sublevels) n=3 = 0, 1, 2 (three sublevels) etc.. In general, number of sublevels = n.

Copyright © 2001 by Harcourt, Inc. All rights reserved The electromagnetic spectrum

Copyright © 2001 by Harcourt, Inc. All rights reserved Sublevel Designations Sublevels designated as: s, p, d, f Value of Lettersp d f Capacity261014

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Copyright © 2001 by Harcourt, Inc. All rights reserved Shapes of p orbitals

Copyright © 2001 by Harcourt, Inc. All rights reserved Shapes of p orbitals

Copyright © 2001 by Harcourt, Inc. All rights reserved Electronic Structure Electronic Configuration : an expression giving the population of electrons in each sublevel. 3rd and 4th Quantum Numbers : direction in space of the electron cloud and electron spin Orbital Diagram

Copyright © 2001 by Harcourt, Inc. All rights reserved Electronic Configuration Indicate by a superscript the number of electrons in each sublevel. H:1s 1 Li:[He]2s 1 Na:[Ne]3s 1 K:[Ar]4s 1 He:1s 2 Be:[He]2s 2 Mg:[Ne]3s 2 Ca:[Ar]4s 2 B:[He]2s 2 2p 1 Al:[Ne]3s 2 3p 1 Sc:[Ar]4s 2 3d 1 ||| Ne:[He]2s 2 2p 6 Ar:[Ne]3s 2 3p 6 | Zn: [Ar]4s 2 3d 10 | Kr:[Ar]4s 2 3d 10 4p 6

Copyright © 2001 by Harcourt, Inc. All rights reserved Sublevels in order of increasing energy

Copyright © 2001 by Harcourt, Inc. All rights reserved Electronic Configuration (cont.) Beyond krypton, it’s best to derive electronic configurations from the periodic table. Groups 1, 2:fill s sublevel Groups 13-18:fill p sublevel Groups 3-12:fill d sublevels Lanthanides and actinides fill f sublevels (4f, 5f)

Copyright © 2001 by Harcourt, Inc. All rights reserved Periodic table and electron configuration

Copyright © 2001 by Harcourt, Inc. All rights reserved Periodic table and electron configuration Group Period

Copyright © 2001 by Harcourt, Inc. All rights reserved Periodic table and electron configuration Group Period

Copyright © 2001 by Harcourt, Inc. All rights reserved Periodic table and electron configuration Group Period

Copyright © 2001 by Harcourt, Inc. All rights reserved rd and 4 th Quantum Numbers Orbital designated by m =, … 1, 0, -1, … - = 0 (s sublevel); m = 0 (one s orbital) = 1 (p sublevel); m = 1, 0, -1 (three p orbitals) = 2 (d sublevel); m = 2, 1, 0, -1, -2 (5 d orbitals)  Each orbital has a capacity of two electrons.  s orbitals are spherically symmetric about the nucleus;  p orbitals are dumbbell shaped and are at right angles to each other.

Copyright © 2001 by Harcourt, Inc. All rights reserved rd and 4 th Quantum Numbers (cont.) As electron has magnetic properties that correspond to those of a charged particle spinning on its axis either clockwise or counterclockwise : m s = +1/2, –1/2

Copyright © 2001 by Harcourt, Inc. All rights reserved Orbital Diagrams Show number of electrons in each orbital and spin of each electron. 1s 2s2p H(  ) He(  ) Li(  )(  ) Be(  )(  ) B(  )(  )(  ) ( ) ( )

Copyright © 2001 by Harcourt, Inc. All rights reserved Orbital Diagrams (cont.) 1s 2s2p C(  (  (  (  (   (  (  (  (  (   (  (  (  (  (  Note that:  2 e - in same orbital have opposed spins  When several orbitals of same sublevel are available, e - enter singly with parallel spins.

Copyright © 2001 by Harcourt, Inc. All rights reserved Orbital Diagrams (cont.) What is the abbreviated electron configuration and orbital diagram of Fe? [Ar]4s 2 3d 6 4s 3d [Ar](  (  (   (   (   (  

Copyright © 2001 by Harcourt, Inc. All rights reserved Monatomic Ions Ions with noble gas structures (Groups 1, 2, 16, 17) by gaining or losing electrons. Electrons are added to or removed from sublevels in the highest principal energy level. Transition metal cations; outer s electrons are lost: 24 Cr 3+ [Ar]3d 3 27 Co 2+ [Ar]3d 7 30 Zn 2+ [Ar]3d 10

Copyright © 2001 by Harcourt, Inc. All rights reserved Species with noble gas structures

Copyright © 2001 by Harcourt, Inc. All rights reserved Trends in the Periodic Table Atomic Radius Ionic Radius Ionization Energy Electronegativity

Copyright © 2001 by Harcourt, Inc. All rights reserved Atomic Radius In general, atomic radius decreases going across a period from left to right, increases going down a group.

Copyright © 2001 by Harcourt, Inc. All rights reserved Sizes of atoms and ions

Copyright © 2001 by Harcourt, Inc. All rights reserved Atomic Radius (cont.) Trends can be explained in terms of effective nuclear charge felt by outer electron(s). Electrons in outer levels do not shield one another effectively.

Copyright © 2001 by Harcourt, Inc. All rights reserved Ionic Radius Trends parallel those in atomic radius. Beyond that:  cations are smaller than corresponding atoms  anions are larger than corresponding atoms This means that, in a typical ionic compound, the anions occupy most of the space.

Copyright © 2001 by Harcourt, Inc. All rights reserved Sizes of atoms and ions

Copyright © 2001 by Harcourt, Inc. All rights reserved Ionization Energy Energy that must be absorbed to convert an atom to a +1 ion. Na(g)  Na + (g) + e - I.E. = +496 kJ/mol  increases going across in periodic table, as atoms get smaller  decreases going down in periodic table, as atoms get larger

Copyright © 2001 by Harcourt, Inc. All rights reserved First ionization energies

Copyright © 2001 by Harcourt, Inc. All rights reserved Electronegativity A property of an atom that increases with its tendency to attract electrons to a covalent bond.  increases going across in periodic table  decreases going down in periodic table