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23.1 Transition Elements.docx

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CHEM 110
Ariel Fenster

23.1 - 23The Formation ofrties of Transition Elements Transition Elements Coordination Compounds The Formation of Coordination Compounds: LewisAcid Lewis Base 2+ 2+ Fe + H O2 Fe(H 2) 6 Coordination Complex Why? Alfred Werner: father of Coordination Chemistry  explained transition metals and their properties as well as the compounds the make Transition Elements: high melting points, good conductors  Elements with have partially filled d-orbitals 24.5 Crystal Field Theory 2 1 Petrucci 24.4: Structures and Shape Liand Example: Sc [Ar] 4s 3d NetralCharacterized by filled s orbitals and subsequent filling of d orbitals Spare Electrons  For the first transition elements (Sc to Zn) electron configuration is usually 4s 3d H2O Exceptions do occur, for example: Chromium (Cr) and Copper (Cu) Alfred Werner (1866 - 1919) Because alternative electron configurations brings more stability to the atom and are Nobel Prize in 1913 for his coordination theory of transitioenergFeically favoredes  Examples: Structure? Metal ion:o Chromium (Cr): 4s 3d but 4s 3d is more stable5 2+ Positively Charged 2 9 1 9 Fe(H2O)6 Short of Eo CoppeMolecules/ions that want electrons react with molecules/ions that have electrons. Transition Element: an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell 24.5 Crystal Field Theory Electron Configuration and Oxidation States:  Any element may display several oxidation states; in crossing the first transition series, the nuclear charge, number of d electrons and energy requirement for the 2 O successive ionization of d electrons increase. H2O H2O  Involvement of a large number of d electrons in bond formation becomes +2+ increasingly unfavorable energetically, and only the lower oxidation states are Fe H2O 2 O commonly encountered for these later elements of first transition series.  The stability of an oxidation state depends on the atoms to which it is bonded, 2 O whether the compound is in solid form or in solution; and the pH of the solution. Most Common Types of Magnetism: Diamagnetism and Paramagnetism Understanding magnetism in transition metal complexes stabilized when oxide or fluoride using our understanding of the bonding Ionization Energies and Electrode Potentials:  Ionization energies are fairly constant across the first transition series  Standard electrode potentials gradually increase in value across the series 2+  With the exception of oxidation of Cu to Cu , all these elements are more readily 2 oxidized with hydrogen (meaning the metals displace H to H ) 2 23.1 - 23.5 General Properties of Transition Elements Ionic and Covalent Compounds:  Transition metals display both ionic and covalent character  Compounds with higher transition metal in lower oxidation states are essentially ionic, while those in higher oxidation states have covalent character  Metal atoms often occur in polyatomic cations or anions rather than as the simple monatomic ion Catalytic Activity:  Good heterogeneous catalysts  transition metals with an unusual ability to absorb gaseous species  Homogeneous catalysis: reactants/products/catalysts are all in the same phase (often liquid or gas), the transition metal atoms or ions serve as electron banks that lend out electrons at the appropriate time or store them for later use  Heterogeneous catalysis: the catalyst is in a different phase from the reactants or the products and typically the catalyst provides a surface on which the reaction occurs Color and Magnetism:  Electronic transitions that occur within the d orbitals impart color to transition compounds and their solutions  Ferromagnetism: the ability to be made into permanent magnets o Key feature: in solid state, the metal atoms are thought to be grouped together into small regions (called domains) containing large numbers of atoms; all magnetic moments are directed in the same way o In paramagnetic material, the effect of a magnetic field is to align the magnetic moments of individual atoms o In ferromagnetic material, the magnetic moments are aligned within domains even in the absence of a magnetic field, however the direction of the alignment varies from one domain to the other What are Transition Metals Useful for; everyday life? The Stone Age: tools made of stone  metals were completely available except for the most precious and expensive metal gold Bronze Age: refers to a period that consists of techniques for smelting copper and tin from naturally occurring ore, making an alloy with these metals to make bronze Iron Age: commonly used for making tools and weapons  mix with a little bit of carbon to make steel (does not rust, very easily available)  Fe alloys (Mn, Ni, Cr, W) Titanium Age: high tensile strength, corrosion resistance and ability to withstand to high temperatures. Titanium alloys are used in aircraft, spacecraft’s, and missiles  Example: the engines of the Airbus uses about 11 tons of titanium 23.1 - 23.5 General Properties of Transition Elements 11/2/2011 Metal Containing Compounds: Photography: Ag (AgBr)  First used in the 1830s by the French inventor Nicephore Niepce as a method of recording the image of an object through
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