Unformatted text preview: Introduction to Many Electron Atoms (n, l, ml) called quantum numbers n is related to the of the orbital l is related to the of the orbital ml relates to the of the orbital ms is the quantum number Pauli Exclusion Principle In many electron atoms, the s, p, d, f, ...subshells are not degenerate: Es < Ep < Ed < Ef (n = const.) degenerate:
9/11/2008 Zumdahl Chapter 12 1 The Periodic Table: Dmitri Ivanovich Mendeleev Mendeleev's Early Periodic Table (1872) Source: Corbis 9/11/2008 Zumdahl Chapter 12 2 1 Many Electron Atoms: The Aufbau Principle Aufbau means " " When several orbitals are equal in energy, the lowest energy configuration is one where as few orbitals as possible are doubly occupied. The lowest energy configuration is one with parallel spins in all singly occupied orbitals. 9/11/2008 Zumdahl Chapter 12 3 Hund's Rules Applied to Carbon When several orbitals are equal in energy, the lowest energy configuration is one where as few orbitals as possible are doubly occupied. The lowest energy configuration is one with parallel spins in all singly occupied orbitals. 9/11/2008 Zumdahl Chapter 12 4 2 "Aufbau" from Hydrogen to Neon Aufbau" 9/11/2008 Zumdahl Chapter 12 5 The Orbitals Filled for Elements in Various Parts of the Periodic Table 9/11/2008 Zumdahl Chapter 12 6 3 9/11/2008 Zumdahl Chapter 12 7 Valence Electrons Occupy the outermost (highest energy) shell of an atom, i.e., beyond the immediately preceding noble-gas configuration 9/11/2008 Zumdahl Chapter 12 8 4 Valence Electrons (con't) Among the s-block and p-block elements, the valence electrons include electrons in s and p subshells only. Among d-block and f-block (transition elements), valence electrons usually consist of electrons in (n + 1)s orbitals plus electrons in unfilled nd and nf subshells. 9/11/2008 Zumdahl Chapter 12 9 Problem Write the valence-electron configuration and state the number of valence electrons in each of the following atoms and ions: (a) Y, (b) Lu, (c) Mg2+
(a) Y (Yttrium): atomic number Z = 39 (b) Lu (Lutetium): Z = 71 (c) Mg2+ (Magnesium (II) ion): Z = 12 9/11/2008 Zumdahl Chapter 12 10 5 Some Subtleties in Ground State Electron Configurations
"Building Up" (Potassium through Gallium) Up"
K: 4s1 Cr: 4s13d5 Cu: 4s13d10 Ca: 4s2 Mn: Mn: 4s23d5 Zn: 4s23d10 Sc: 4s23d1 Fe: 4s23d6 Ga: 4s23d104p1 Ga: Ti: 4s23d2 Co: 4s23d7 V: 4s23d3 Ni: 4s23d8 "Tearing Down" (Ground State Ions) Down"
Ga : 4s23d104p1 Ga+: 4s23d10 Ga2+: 4s13d10 Ga3+: 3d10 Cr: 4s13d5 Cr+: 3d5 V: 4s23d3 V+: 4s13d3 V2+: 3d3 As Z increases, transfer of a 4s electron to a 3d orbital becomes more favorable because the electronbecomes electronelectron repulsions are compensated by attractive interactions between the nucleus and electrons in between the more spatially compact 3d orbital. Hence, all M2+ cations of Sc through Zn have [Ar]4s03dn configurations
9/11/2008 Zumdahl Chapter 12 11 Periodic Trends in Atomic Properties Ionization Energy Electron Affinity Atomic Radius 9/11/2008 Zumdahl Chapter 12 12 6 The ionization energy (IE of an atom is the minimum amount of IE) energy necessary to detach an electron from a ground state atom. 9/11/2008 Zumdahl Chapter 12 13 9/11/2008 Zumdahl Chapter 12 14 7 Electron Affinity (EA) Because of stability of closed shell structures, EA tends to parallel IE but is shifted one atomic number lower, e.g., 9/11/2008 Zumdahl Chapter 12 15 Atomic Radius
The radius of an atom (r) is defined as 9/11/2008 Zumdahl Chapter 12 16 8 Atomic radii (in picometers) for selected atoms 9/11/2008 Zumdahl Chapter 12 17 Sizes of Atoms
Atomic size generally moving down a group Among s-block and p-block elements, atomic size generally moving from left to right 9/11/2008 Zumdahl Chapter 12 18 9 Special Names for Groups in the Periodic Table 9/11/2008 Zumdahl Chapter 12 19 Special Names for Groups in the Periodic Table (con't) con' 9/11/2008 Zumdahl Chapter 12 20 10 Chapter 12 Quantum Mechanics and Atomic Theory
12.1 12.2 12.3 12.4 12.5 12.6 12.7 12.8 12.9 12.10 12.11 12.12 12.13 12.14 12.15 12.16 Electromagnetic Radiation The Nature of Matter The Atomic Spectrum of Hydrogen The Bohr Model The Quantum Mechanical Description of the Atom The Particle in a Box (skip) The Wave Equation for the Hydrogen Atom The Physical Meaning of a Wave Function The Characteristics of Hydrogen Orbitals Electron Spin and the Pauli Principle Polyelectronic Atoms The History of the Periodic Table The Aufbau Principle and the Periodic Table Further Development of the Polyelectronic Model Periodic Trends in Atomic Properties The Properties of a Group: The Alkali Metals
Zumdahl Chapter 12 21 9/11/2008 11 ...
View Full Document