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Chapter 24 Transition Metals & Coordination Compounds. 24.2 Properties of Transition Metals Review Electron Configuration Trends in the Periodic Table 24.3 Coordination Compounds The Basics Example of Naming 24.4 Structure and Isomerization.
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Chapter 24Transition Metals &Coordination Compounds • 24.2 Properties of Transition Metals • Review Electron Configuration • Trends in the Periodic Table • 24.3 Coordination Compounds • The Basics • Example of Naming • 24.4 Structure and Isomerization
Transition Metals contain e- in d Orbitals http://www.can-do.com/uci/lessons98/Periodic.html http://www.can-do.com/uci/lessons98/Periodic.html
Why Are Transition Metals & Coordination Compounds Important? • Therapeutic drugs • Chemical Sensors • Coloring agents • Paints • Cosmetics • Biological Molecules • Hemeglobin • Chlorophyll • Gems (Jewelry & Technological Applications) • Rubies, Emeralds, Garnets, etc. • Lasers
24.2 Properties of Transition Metals • Moderate to High Densities • Good Electrical Conductivity • High Melting Points • Moderate to Extreme Hardness Due to the delocalization of d electrons in metallic bonding Exceptions: Elements with filled d orbitals, which prevents d-d bonding. Hg has a low melting point and is liquid at room temperature. http://www.tutorvista.com/chemistry/shapes-of-d-orbitals
Electron Configuration Increasing Energy (n-1)d (n-2)f
Electron Configuration [noble gas] ns2 (n-1)dx [noble gas] ns2 (n-2)f14 (n-1)dx
Electron Configuration [Kr] 5s2 4d2 http://malaxoschemistry.wikispaces.com/Periodic+Table
Atomic Size Decreasing Size Increas Ing S i ze http://malaxoschemistry.wikispaces.com/Periodic+Table
Atomic Size Exception to the trend: Electrons in the f-orbitals are not effective at shielding outer shell electrons from nuclear charge. So, the outer electrons are held in close – this is known as lanthanide contraction.
Ionization Energy Increases Decreases http://malaxoschemistry.wikispaces.com/Periodic+Table
Ionization Energy Exception to the trend: Note that 5d elements have a greater ionization energy. This is again due to outer shell electron being held closer to the nucleus, so it take more energy to pull them away.
Electronegativity Increases Decreases http://malaxoschemistry.wikispaces.com/Periodic+Table
Electronegativity Au: EN = 2.4 Compared to P: EN = 2.1 !! Exception to the trend: There is an increase in electronegativity from the 3d (1st row transition metals) to the 4d (2nd row transition metals).
Oxidation States In general, stability is found in full or half-full shells, and in a configuration that looks like a noble gas.
24.3 Coordination Compounds • Complex Ion - Central Metal bound to one or more ligands • Ligands are Lewis Base* (electron donors) and can be either neutral or negatively charged • The charge on the complex ion is balance by counter ions of opposite charge The combination of a complex ion and counter ions results in a coordination compound *Corrected 4/15/11 @ 2:30 pm) David N. Blauch - http://www.chm.davidson.edu/vce/index.htm
A Little Background • In 1893, Swiss chemist Alfred Werner came up with the idea that a central metal could have 2 types of interactions • Primary Valence – Oxidation State of the central metal • Secondary Valence – Number of molecules or ions directly attached to the central metal or CoordinationNumber • Example: [Co(NH3)6]Cl3 • The Primary Valence or Oxidation State of Co is +3 • The Secondary Valence or Coordination Number is 6 (6 ammonia ligands are directly attached to Co • Other cobalt(III) coordination compounds • [Co(NH3)6]Cl3 • [Co(NH3)5Cl]Cl2 • [Co(NH3)4Cl2]Cl
Coordinate Covalent Bonds • Lewis Acid-Base Adduct – the ligand donates it’s electrons to the empty metal orbitals to form a coordinate covalent bond M : L Lewis Base Lewis Acid Adduct
Chelating Agents • Ligands can have one or more bonding pairs of electrons • Monodentate • Bidentate or Polydentate • Complex ions with bidentate or polydentate ligands are chelates, and the coordinating ligands are chelating agents Co EDTA is hexadentate http://library.kiwix.org:4201/A/Inorganic_chemistry.htm
Geometries Anne Marie Helmenstine, Ph.D., About.comGuide
Naming Coordination Compounds • [Mn(CO)(NH3)5]SO4 (neutral ligands are written before charged ligands in the formula) • Cation 1st • Name the ligands in alphabetical order • ammine • carbonyl • Add a prefix to indicate the number of ligands • pentaammine • Name the metal ion • Manganese(II) • Anion 2nd • Sulfate • Pentaamminecarbonylmanganese(II) sulfate
24.4 Structure & Isomerism Same formula – different structures Same connectivities –different spacial arrangements Different connectivities Ligands & counter ions trade places Ligands coordinate in different ways Different spacial arrangements Mirror images
Structural IsomersCoordination Isomers pentaamminesulfatochromium(III) bromide pentaamminebromochromium(III) sulfate David N. Blauch - http://www.chm.davidson.edu/vce/index.htm
Structural IsomersLinkage Isomers pentaamminenitrocobalt(III) ion pentaamminenitritocobalt(III) ion David N. Blauch - http://www.chm.davidson.edu/vce/index.htm
StereoisomersGeometric Isomers: cis-trans cis trans cis-diamminedichloroplatinum(II) trans-diamminedichloroplatinum(II) David N. Blauch - http://www.chm.davidson.edu/vce/index.htm
StereoisomersGeometric Isomers: fac-mer fac mer fac-triamminetrichlorocobalt(III) mer-triamminetrichlorocobalt(III) David N. Blauch - http://www.chm.davidson.edu/vce/index.htm
StereoisomersOptical Isomers • Mirror Images • Non-superimposable • Enantimomers • Chiral: optically active (rotates polarized light) http://www.wikidoc.org/index.php/Chirality_%28chemistry%29 http://en.wikipedia.org/wiki/Chirality_%28electromagnetism%29
ChiralityDetermining Optical Activity fac mer David N. Blauch - http://www.chm.davidson.edu/vce/index.htm
ChiralityDetermining Optical Activity Superimposable - No optical activity