General Chemistry: An Integrated Approach Hill, Petrucci, 4th Edition Chapter 8 Electron Configurations, Atomic Properties, and the Periodic Table Mark P. Heitz State University of New York at Brockport © 2005, Prentice Hall, Inc.

Multielectron Atoms Electrons are attracted to the nucleus while simultaneously repelling one another EOS In the hydrogen atom, all subshells of a principal shell are at the same energy level recall En = –B/n2 Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Multielectron Atoms In a multielectron atom the various subshells of a principal shell are at different energy levels, but all orbitals within a subshell are at the same energy level The increasing energy order of subshells is generally: s < p < d < f EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Multielectron Atoms Orbital energies are lower in multielectron atoms than in the hydrogen atom In higher numbered principal shells of a multielectron atom, some subshells of different principal shells have nearly identical energies EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Electron Configurations Electron configuration describes the distribution of electrons among the various orbitals in the atom The spdf notation uses numbers to designate a principal shell and the letters to identify a subshell; a superscript number indicates the number of electrons in a designated subshell EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Formula Mass An orbital diagram uses boxes to represent orbitals within subshells and arrows to represent electrons: EOS Each box has arrows representing electron spins; opposing spins are paired together Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Rules for Electron Configurations Electrons occupy the lowest available energy orbitals Pauli exclusion principle – no two electrons in the same atom may have the same four quantum numbers EOS Orbitals hold a maximum of two electrons spins must be opposed Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Rules for Electron Configurations For orbitals of identical energy, electrons enter empty orbitals whenever possible – Hund’s rule Electrons in half-filled orbitals have parallel spins EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Rules for Electron Configurations Capacities of shells (n) and subshells (l) EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Rules for Electron Configurations Subshell filling order ... Each subshell must be filled before moving to the next level EOS 1s22s22p63s23p6 ... Illustration Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

The Aufbau Principle A hypothetical building up of an atom from the one that precedes it in atomic number (Z = 1) H 1s1 (Z = 2) He 1s2 (Z = 3) Li 1s22s1 EOS (Z = 3) Li 1s22s1  [He]2s1 Abbreviated electron configuration Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

The Aufbau Principle ... [He]2p2 [He]2p3 [He]2p4 [He]2p5 [He]2p6 EOS [He]2p6 Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Main Group and Transition Elements Elements in which the orbitals being filled in the aufbau process are either s or p orbitals of the outermost shell are called main group elements “A” group designation on the periodic table The first 20 elements are all main group elements In transition elements, the subshell being filled in the aufbau process is in an inner principal shell EOS Fourth period transition elements have n = 4 as their outermost shell as the 3d subshell fills Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Main Group and Transition Elements Completely filled and half-filled sublevels are more energetically favorable configurations EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Periodic Relationships The valence shell is the outermost occupied shell The period number = principal quantum number, n, of the electrons in the valence shell EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Periodic Relationships For main group elements the number of valence shell electrons is the same as the periodic table “A” group number EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Periodic Relationships We can deduce the general form of electron configurations directly from the periodic table EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Valence Electrons and Core Electrons Valence electrons are those with the highest principal quantum number EOS Sulfur has six valence electrons Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Valence Electrons and Core Electrons Electrons in inner shells are called core electrons EOS Sulfur has 10 core electrons Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Electron Configurations of Ions Anions: gain e– to complete the valence shell Example: EOS - Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Electron Configurations of Ions Cations: lose e– to attain a complete valence shell Example: (Z = 11) Na EOS (Z = 11) Na+ Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Electron Configurations of Ions Cations formed from transition metals lose e– from the highest principal energy level (n) EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Magnetic Properties Diamagnetism is the weak repulsion associated with paired electrons Paramagnetism is the attraction associated with unpaired electrons EOS Ferromagnetism is the exceptionally strong attractions of a magnetic field for iron and a few other substances Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Periodic Atomic Properties of the Elements Periodic law states that certain sets of physical and chemical properties recur at regular intervals when the elements are arranged according to increasing atomic number EOS Consider atomic radii: distance between the nuclei of two atoms Periodic Properties Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Atomic Radii Properties Illustration EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Ionic Radii The ionic radius of each ion is the portion of the distance between the nuclei occupied by that ion EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Ionic Radii Cations are smaller than the atoms from which they are formed – the nucleus attracts the remaining electrons more strongly EOS Anions are larger than the atoms from which they are formed – the greater number of electrons repel more strongly Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Isoelectronic Configurations = elements that all have the same number of electrons For isoelectronic species, the greater the nuclear charge, the smaller the species Effective nuclear charge EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Atomic and Ionic Radii EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Ionization Energy Ionization energy is the energy required to remove an electron from a ground state atom in the gaseous state Continual removal of electrons increases ionization energy greatly B  B+ + e– I = 801 kJ mol–1 B+  B+2 + e– I = 2427 kJ mol–1 B+2  B+3 + e– I = 3660 kJ mol–1 B+3  B+4 + e– I = 25,025 kJ mol–1 Illustration EOS B+4  B+5 + e– I = 32,822 kJ mol–1 Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

First Ionization Energies Illustration EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Electron Affinity Electron affinity is the energy change that occurs when an electron is added to a gaseous atom EOS Electron affinities are expressed as negative because the process is exothermic Illustration Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Metals, Nonmetals, and Metalloids Metals have a small number of electrons in their valence shells and tend to form positive ions Except for hydrogen and helium, all s-block elements are metals EOS All d- and f-block elements are metals Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Metals, Nonmetals, and Metalloids Atoms of a nonmetal generally have larger numbers of electrons in their valence shell than do metals, and many tend to form negative ions Nonmetals are all p-block elements and include hydrogen and helium EOS Metalloids have properties of both metals and nonmetals Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

A Summary of Periodic Trends EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

The Inert (Noble) Gases The six noble gases, He, Ne, Ar, Kr, Xe, and Rn, rarely enter into chemical reactions All have complete octets ... = stability! EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

“Periodic” Behavior of Elements Flame tests: elements with low first ionization energies are excited in a flame EOS Atoms emit energy when electrons fall from higher to lower energy states FlameTests Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

“Periodic” Behavior of Elements halogens (Group 7A) are good oxidizing agents EOS When Cl2 is bubbled in a solution containing iodide ions, chlorine oxidizes I– to I2 Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

The s-Block Metals as Reducing Agents 2 K + 2 H2O  2 K+ + 2 OH– + H2 EOS Recall activity series ... H+ is reduced by these metals Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Acidic, Basic, and Amphoteric Oxides Acidic oxides are oxides that produce acids by reacting the oxide with water e.g., SO3 + H2O  H2SO4 EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Acidic, Basic, and Amphoteric Oxides Basic oxides are oxides that produce bases by reacting with water e.g., MgO + H2O  Mg(OH)2 EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Acidic, Basic, and Amphoteric Oxides Oxides that can react with either acids or bases are amphoteric oxides e.g., Al2O3 Behavior of Oxides EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Summary of Concepts The wave-mechanical treatment of the hydrogen atom can be extended to multielectron atoms, but with two differences Electron configuration is the distribution of electrons in orbitals among the subshells and principal subshells EOS There are two types of electron configuration notation: spdf and orbital Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Summary of Concepts The aufbau principle describes a process of hypothetically building up an atom from the atom of the preceding atomic number Elements in similar electron configurations fall in the same group of the periodic table An atom with all the electrons paired is diamagnetic; an atom with one or more unpaired electrons is paramagnetic EOS Certain atomic properties, such as atomic radius, ionic radius, ionization energy, and electron affinity, vary periodically with increasing atomic number Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table

Summary of Concepts The regions of the periodic table ascribed to metals, nonmetals, metalloids, and the noble gases are related to the value of atomic properties EOS Chapter 8: Electron Configurations, Atomic Properties and the Periodic Table