Atomic Electron Configurations and Chemical Periodicity Chapter 8 Atomic Electron Configurations and Chemical Periodicity Dr. S. M. Condren

ATOMIC ELECTRON CONFIGURATIONS AND PERIODICITY Dr. S. M. Condren

Atomic Orbitals Types of orbitals found in the known elements: s, p, d, and f schools play defensive football Packer version: secondary pass defense fails Dr. S. M. Condren

Atomic Orbitals Shapes s – spherical p – dumbbell d – complex f – very complex Dr. S. M. Condren

Arrangement of Electrons in Atoms Electrons in atoms are arranged as SHELLS (n) SUBSHELLS (l) ORBITALS (ml) Dr. S. M. Condren

Arrangement of Electrons in Atoms Each orbital can be assigned no more than 2 electrons! This is tied to the existence of a 4th quantum number, the electron spin quantum number, ms. Dr. S. M. Condren

Electron Spin Quantum Number, ms Can be proved experimentally that electron has a spin. Two spin directions are given by ms where ms = +1/2 and -1/2. Dr. S. M. Condren

Electron Spin and Magnetism Diamagnetic: NOT attracted to a magnetic field Paramagnetic: substance is attracted to a magnetic field. Substances with unpaired electrons are paramagnetic. Dr. S. M. Condren

Measuring Paramagnetism Paramagnetic: substance is attracted to a magnetic field. Substance has unpaired electrons. Diamagnetic: NOT attracted to a magnetic field Dr. S. M. Condren Active Figure 8.2

QUANTUM NUMBERS Now there are four! n ---> shell 1, 2, 3, 4, ... l ---> subshell 0, 1, 2, ... n - 1 ml ---> orbital -l ... 0 ... +l ms ---> electron spin +1/2 and -1/2 Dr. S. M. Condren

Pauli Exclusion Principle No two electrons in the same atom can have the same set of 4 quantum numbers. That is, each electron has a unique address. Dr. S. M. Condren

Electrons in Atoms When n = 1, then l = 0 this shell has a single orbital (1s) to which 2e- can be assigned When n = 2, then l = 0, 1 2s orbital 2e- three 2p orbitals 6e- TOTAL = 8e- Dr. S. M. Condren

Electrons in Atoms When n = 3, then l = 0, 1, 2 3s orbital 2e- three 3p orbitals 6e- five 3d orbitals 10e- TOTAL = 18e- Dr. S. M. Condren

Electrons in Atoms When n = 4, then l = 0, 1, 2, 3 4s orbital 2e- three 4p orbitals 6e- five 4d orbitals 10e- seven 4f orbitals 14e- TOTAL = 32e- And many more! Dr. S. M. Condren

Dr. S. M. Condren

Assigning Electrons to Atoms Electrons generally assigned to orbitals of successively higher energy. For H atoms, E = - C(1/n2). E depends only on n. For many-electron atoms, energy depends on both n and l. Dr. S. M. Condren

Electron Filling Order Dr. S. M. Condren

LED Traffic Lights http://mrsec.wisc.edu/Edetc/background/LED/traffic_light/index.htm Chapter 7, Problem 3, page 326 text Dr. S. M. Condren

Writing Atomic Electron Configurations Two ways of writing configs. One is called the spdf notation. 1 s value of n value of l no. of electrons spdf notation for H, atomic number = 1 Dr. S. M. Condren

Writing Atomic Electron Configurations Other is called the orbital box notation One electron has n = 1, l = 0, ml = 0, ms = + 1/2 Other electron has n = 1, l = 0, ml = 0, ms = - 1/2 Dr. S. M. Condren

See “Toolbox” on CD for Electron Configuration tool. Dr. S. M. Condren

Electron Configurations and the Periodic Table Dr. S. M. Condren

Lithium Group 1A Atomic number = 3 1s22s1 ---> 3 total electrons Dr. S. M. Condren

Beryllium Group 2A Atomic number = 4 1s22s2 ---> 4 total electrons Dr. S. M. Condren

Boron Group 3A Atomic number = 5 1s2 2s2 2p1 ---> 5 total electrons Dr. S. M. Condren

Carbon Group 4A Atomic number = 6 1s2 2s2 2p2 ---> 6 total electrons Here we see for the first time HUND’S RULE. When placing electrons in a set of orbitals having the same energy, we place them singly as long as possible. Dr. S. M. Condren

Nitrogen Group 5A Atomic number = 7 1s2 2s2 2p3 ---> 7 total electrons Dr. S. M. Condren

Oxygen Group 6A Atomic number = 8 1s2 2s2 2p4 ---> 8 total electrons Dr. S. M. Condren

Fluorine Group 7A Atomic number = 9 1s2 2s2 2p5 ---> 9 total electrons Dr. S. M. Condren

Neon Group 8A Atomic number = 10 1s2 2s2 2p6 ---> 10 total electrons Note that we have reached the end of the 2nd period, and the 2nd shell is full! Dr. S. M. Condren

Sodium Group 1A Atomic number = 11 1s2 2s2 2p6 3s1 or “neon core” + 3s1 [Ne] 3s1 (uses rare gas notation) Note that we have begun a new period. All Group 1A elements have [core]ns1 configurations. Dr. S. M. Condren

Aluminum Group 3A Atomic number = 13 1s2 2s2 2p6 3s2 3p1 [Ne] 3s2 3p1 All Group 3A elements have [core] ns2 np1 configurations where n is the period number. Dr. S. M. Condren

Phosphorus Group 5A Atomic number = 15 1s2 2s2 2p6 3s2 3p3 Yellow P Red P Group 5A Atomic number = 15 1s2 2s2 2p6 3s2 3p3 [Ne] 3s2 3p3 All Group 5A elements have [core ] ns2 np3 configurations where n is the period number. Dr. S. M. Condren

Calcium Group 2A Atomic number = 20 1s2 2s2 2p6 3s2 3p6 4s2 [Ar] 4s2 All Group 2A elements have [core]ns2 configurations where n is the period number. Dr. S. M. Condren

Transition Metals Table 8.4 All 4th period elements have the configuration [argon] nsx (n - 1)dy and so are d-block elements. Chromium Iron Copper Dr. S. M. Condren

Transition Element Configurations 3d orbitals used for Sc-Zn (Table 8.4) Dr. S. M. Condren

Dr. S. M. Condren

Board Work V – electron configuration Cr – electron configuration Mn – electron configuration Ni – electron configuration Cu – electron configuration Zn – electron configuration Dr. S. M. Condren

Magnetism Paramagnetism Ferromagnetism Spins are randomized by thermal energy. Spins are aligned with or against an applied magnetic field. Ferromagnetism Spins are aligned with an applied magnetic field. Spins are ordered in magnetic domains. Dr. S. M. Condren

NMR and MRI http://mrsec.wisc.edu/Edetc/background/NMR/index.html Nuclei also have spin and nuclear quantum numbers 800 MHz, 18.8 T NMR spectrometer Open Magnet Design MRI http://mrsec.wisc.edu/Edetc/background/NMR/index.html http://mrsec.wisc.edu/Edetc/cineplex/NMR/index.html Dr. S. M. Condren

Memory Metal Dr. S. M. Condren

Nitinol, NiTi http://mrsec.wisc.edu/Edetc/background/memmetal/index.html Dr. S. M. Condren

Lanthanides and Actinides All these elements have the configuration [core] nsx (n - 1)dy (n - 2)fz and so are f-block elements. Cerium [Xe] 6s2 5d1 4f1 Uranium [Rn] 7s2 6d1 5f3 Dr. S. M. Condren

Lanthanide Element Configurations 4f orbitals used for Ce - Lu and 5f for Th - Lr (Table 8.2) Dr. S. M. Condren

Dr. S. M. Condren

Ion Configurations To form cations from elements remove 1 or more e- from subshell of highest n [or highest (n + l)]. P [Ne] 3s2 3p3 - 3e- ---> P3+ [Ne] 3s2 3p0 Dr. S. M. Condren

Ion Configurations For transition metals, remove ns electrons and then (n - 1) electrons. Fe [Ar] 4s2 3d6 loses 2 electrons ---> Fe2+ [Ar] 4s0 3d6 To form cations, always remove electrons of highest n value first! http://mrsec.wisc.edu/Edetc/cineplex/ff/index.html Dr. S. M. Condren

Quantum Numbers What is one of the sets of quantum numbers for the 4s electrons in calcium? n = 4; l = 0; ml = 0; s = +1/2 or n = 4; l = 0; ml = 0; s = -1/2 Dr. S. M. Condren

Quantum Numbers What is one of the sets of quantum numbers for the 3p electrons in sulfur? n = 3; l = 1; ml = +1; s = +1/2 or n = 3; l = 1; ml = +1; s = -1/2 or n = 3; l = 1; ml = 0; s = +1/2 or n = 3; l = 1; ml = 0; s = -1/2 or n = 3; l = 1; ml = -1; s = +1/2 or n = 3; l = 1; ml = -1; s = -1/2 Dr. S. M. Condren

Quantum Numbers What is one of the sets of quantum numbers for the 3d electrons in Fe? n = 3; l = 2; ml = +2; s = +1/2 or n = 3; l = 2; ml = +2; s = -1/2 or n = 3; l = 2; ml = +1; s = +1/2 or n = 3; l = 2; ml = +1; s = -1/2 or n = 3; l = 2; ml = 0; s = +1/2 or n = 3; l = 2; ml = 0; s = -1/2 or n = 3; l = 2; ml = -1; s = +1/2 or n = 3; l = 2; ml = -1; s = -1/2 or n = 3; l = 2; ml = -2; s = +1/2 or n = 3; l = 2; ml = -2; s = -1/2 Dr. S. M. Condren

Announcements You may bring a 4x6 index card with information A periodic table and a table of thermodynamic data will be furnished. You need to know your TAs name and your section number. Photo ID will be required when submitting your exam. Dr. S. M. Condren

Announcements General Chemistry 103 Hour Exam 2 Nov. 6, 2006 Teaching Assistant _________________________ Section _____ Name _________________________________ c General Chemistry 103 Hour Exam 2 Nov. 6, 2006 ALL WORK MUST APPEAR ON TEST FOR ANY CREDIT. Work includes “stating the question in a mathematical form.” A box should be drawn around the answer to be graded for a problem. Dr. S. M. Condren

Announcements Last day to drop Suzie and Christie have papers to return, please see them after class Dr. S. M. Condren

Bonus Points Exam II – worth 105 points, count as 100 5 pts - Available through “Other Lecture Documents” this week, due Friday Nov. 10 Exam III – worth 105 points, count as 100 5 pts - Available through “Other Lecture Documents” later, due Friday Dec. 15 Dr. S. M. Condren

Ion Configurations How do we know the configurations of ions? Determine the magnetic properties of ions. Sample of Fe2O3 Sample of Fe2O3 with strong magnet Dr. S. M. Condren

General Periodic Trends Atomic and ionic size Ionization energy Electron affinity Higher effective nuclear charge Electrons held more tightly Larger orbitals. Electrons held less tightly. Dr. S. M. Condren

Effective Nuclear Charge, Z* Atom Z* Experienced by Electrons in Valence Orbitals Li +1.28 Be ------- B +2.58 C +3.22 N +3.85 O +4.49 F +5.13 Increase in Z* across a period [Values calculated using Slater’s Rules] Dr. S. M. Condren

Orbital Energies Orbital energies “drop” as Z* increases Dr. S. M. Condren

Atomic Radii Dr. S. M. Condren

Atomic Size Size goes UP on going down a group. Because electrons are added further from the nucleus, there is less attraction. Size goes DOWN on going across a period. Dr. S. M. Condren

Atomic Radius Increase in Z* Size decreases across a period owing to increase in Z*. Each added electron feels a greater and greater + charge. Large Small Increase in Z* Dr. S. M. Condren

Trends in Atomic Size Dr. S. M. Condren

Sizes of Transition Elements 3d subshell is inside the 4s subshell. 4s electrons feel a more or less constant Z*. Sizes stay about the same and chemistries are similar! Dr. S. M. Condren

Density of Transition Metals 6th period 5th period 4th period Dr. S. M. Condren

Ion Sizes Does the size go up or down when losing an electron to form a cation? Dr. S. M. Condren

Ion Sizes CATIONS are SMALLER than the atoms from which they come. Li + , 78 pm 2e and 3 p Forming a cation. Li,152 pm 3e and 3p CATIONS are SMALLER than the atoms from which they come. The electron/proton attraction has gone UP and so size DECREASES. Dr. S. M. Condren

Ion Sizes Does the size go up or down when gaining an electron to form an anion? Dr. S. M. Condren

Ion Sizes ANIONS are LARGER than the atoms from which they come. Forming an anion. F - , 133 pm 10 e and 9 p F, 71 pm 9e and 9p ANIONS are LARGER than the atoms from which they come. The electron/proton attraction has gone DOWN and so size INCREASES. Trends in ion sizes are the same as atom sizes. Dr. S. M. Condren

Trends in Ion Sizes Dr. S. M. Condren

Trends in Ionization Energy Dr. S. M. Condren

2nd IE / 1st IE Li Na K B Al Dr. S. M. Condren

Electron Affinity A few elements GAIN electrons to form anions. Electron affinity is the energy involved when an atom gains an electron to form an anion. A(g) + e- ---> A-(g) E.A. = ∆E Dr. S. M. Condren

Electron Affinity of Oxygen ∆E is EXOthermic because O has an affinity for an e-. [He]   O atom + electron O [He]   - ion EA = - 141 kJ Dr. S. M. Condren

Electron Affinity of Nitrogen [He]   N atom ∆E is zero for N- due to electron-electron repulsions. + electron [He]   N- ion EA = 0 kJ Dr. S. M. Condren

Announcements You may bring a 4x6 index card with information A periodic table and a table of thermodynamic data will be furnished. You need to know your TAs name and your section number. Photo ID will be required when submitting your exam. Dr. S. M. Condren

Announcements Last day to drop Suzie and Christie have papers to return, please see them after class Dr. S. M. Condren