Chemistry- JIB T10 Transition Metals

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  • Answers: +3, +2, +3, +2

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  • 1. Chapter ____
  • 2.
    • Complexes: assemblies of a central metal ion bonded to a group of surroundings molecules or ions. Ex. [Ag(NH 3 ) 2 ] +
    • Complex Ion: If the complex carries a charge
    • Coordination Compounds: Compounds that contain complexes
  • 3.
    • Ligands: the molecules or ions that surround the metal ion in a complex and usually have at least one lone pair of electrons
      • Ex. The 2 NH 3 ligands bonded to the Ag +
    • Coordination Number: The number of donor atoms attached to a metal
  • 4.
    • Form one or more stable ions that have a complete d orbitals
      • Recall how to write electron configurations for d orbital elements.
    • Block 2B will not be considered because its only common oxidation state has a complete d orbital
    • ‘ S’ electrons are the first to be removed when these metals form ions
    • Atomic radius: decreases across the period because the 3d electrons shield the 4s electrons
  • 5.
    • Electronegativity & Ionization energy: increases slightly
    • Closed packed structure and a very small atomic radii
      • Results in a very strong metallic bond
      • Leads to transition metals have higher densities, melting points, and boiling points.
    • Form a variety of oxidation states in their compounds
  • 6. Metal +1 +2 +3 +4 +5 +6 +7 Sc Colorless Ti Violet Colorless V Violet Green blue Yellow Cr Blue Green Yellow (CrO 4 2- ) orange (Cr 2 O 7 2- Mn Pale pink Brown Dark green (MnO 4 2- ) Intense purple (MnO 4 - ) Fe Pale green Yellow or brown Co Pink Orange/yellow Ni Green Cu Blue Zn colorless
  • 7.
    • They are either polar or anions
    • Because ligands have lone pairs, they can function as Lewis bases
      • This makes the metal a Lewis acid
    • Ligand coordiante to the metal
      • Ex. [Cu(NH 3 ) 4 ]SO 4 [Cu(NH 3 ) 4 ] 2+ CATION
            • SO 4 2- ANION
  • 8.
    • The charge of a complex is the sum of the charges on the central atom on its surrounding ligands.
    • Try these: What is the oxidation number of the central atom in
    • [Co(NH 3 ) 5 Cl](NO 3 ) 2
    • [Ru(NH 3 ) 5 (H 2 O)]Cl 2
    • [Cr(NH 3 ) 6 ](NO 3 ) 3
    • K 4 [Fe(CN) 6 ]
  • 9.
    • The atom of the ligand bound directly to the metal is called the donor atom
      • Ex. [Ag(NH 3 ) 2 ] + N is the donor atom
    • The coordination number (the number of donor atoms attached to the metal) in the above example is 2.
    • Dependent on the number of donor atoms present, ligands are classified as monodentate, bidentate, or polydentate
      • Ex. Monodentate: H 2 O
    • Bidentate: ethylenediamine: H 2 N-CH 2 –CH 2 –NH 2
    • Bidentate and polydentate ligands are called chelating agents :
      • They hold the metal atom like a claw.
  • 10.
    • In naming salts, the name of the cation is given before the name of the anion.
      • Ex. In [Co(NH 3 ) 5 Cl]Cl 2 , we name the [Co(NH 3 ) 5 Cl] 2+ and then Cl - .
    • Within a complex ion or molecule, the ligands are named before the metal. Prefixes that give the number of ligands are not considered part of the ligand name in determining alphabetical order.
      • In [Co(NH 3 ) 5 Cl] 2+ ion, the ammonia ligands are named first, then the chloride, then the metal: Pentaaminechlorocobalt (III)
  • 11. 3. The names of anionic ligands end in the letter O, whereas neutral ones ordinarily bears the name of the molecule. Number of Ligands Prefix 1 Mono 2 Di 3 Tri 4 Tetra 5 Penta 6 Hexa Ligand Name Cl - Chloro OH - Hydroxo NO 2 - Nitrito CN - Cyano SO 4 2- Sulfato H 2 O Aquo or aqua NH 3 Ammine CO Carbonyl NO Nitrosyl
  • 12.
    • A Greek prefix is used to indicate the number of each kind of ligand when more than one is present. If the name of the ligand itself contains a Greek prefix, such as mono- or di-, the name of the ligand is enclosed in parentheses and alternate prefixes are used, Bis-, Tris-, tetrakis-,hexakis
    • Ex. [Co(en) 3 ]Cl 3 tris(ethylenediamine)cobalt (III) chloride
    • If the complex is an anion, its name ends in –ate.
    • Ex. K 4 [Fe(CN) 6 ] hexocyanoferrate (II) ion
    • Others: Copper: Cuprate
    • Silver: Argenate
  • 13.
    • The oxidation number of the metal is given in parentheses in Roman numerals following the name of the metal.
    • Try naming these:
    • [Cr(H 2 O) 4 Cl 2 ]Cl
    • [Co(NH 3 ) 4 (H 2 O)CN]Cl 2
    • Na[Al(OH) 4 ]
    • K 2 [Ni(CN) 4 ]
    • (NH 4 ) 2 [CuBr 4 ]
    • [Ni(H 2 O) 6 ]SO 4
    • [CoCl 3 (NH 3 ) 3 ] 1-
    • [Co(NH 3 ) 6 ]Cl 3
    • K 3 [Fe(CN) 6 ]
    • K 4 [Fe(CN) 6 ]
  • 14. ☺ Central ion is first ☺ Ligands second ☺ Neutral molecules first ☺ Negative ions second ☺ Neutral molecules and polyatomic ions are always surrounded by (parentheses) , even if only 1 present ☺ Entire complex ion formula surrounded by [brackets]
  • 15. Write the formula for the diamminepalladium(II) ion ☺ Central ion – palladium (Pd) ☺ Ligands – NH 3 (2) ☺ Written in parentheses ☺ Neutral charge ☺ Brackets around entire formula ☺ Calculate the net charge [Pd(NH 3 ) 2 ] 2+
  • 16. Write the formula for the carbonylpentacyanoferrate(II) ion ☺ Central ion – iron (Fe) ☺ Ligands ☺ CN (5) 1- charge Written in parentheses ☺ CO (1) Neutral Written in parentheses ☺ Brackets around entire formula ☺ Calculate the net charge [Fe(CO)(CN) 5 ] 3-
  • 17.
    • Tetraammineplatinum(II) ion
      • [Pt(NH 3 ) 4 ] 2+
    • Tetraiodoaurate(III) ion
      • [AuI 4 ] -
    • Pentacarbonylnitrosyliron(II) ion
            • [Fe(CO) 5 (NO)] 2+
  • 18.
    • Ligand Exchange Reactions of Transition Metals (and Al 3+ )
      • Complex ions undergo ligand substitution reactions in solutions
      • Ex. [Ni(H 2 O) 6 ] 2+ + NH 3 -> [Ni(NH 3 ) 6 ] 2+ + H 2 O or
      • Ni 2+ + NH 3 -> [Ni(NH 3 ) 6 ] 2+
    • How do you know the number of ligands that are in the product?
      • Hint: Often, not all the time!!, the number of ligands is twice the cation charge.
      • Also, helpful to know the following table
  • 19. Metal Ion Ligand Number of Ligands Fe 3+ SCN - 1 Ni 2+ NH 3 Any between 1 and 6 Ag + CN - 2 Ag + NH 3 1 or 2 Zn 2+ NH 3 4 Al 3+ OH - 3 or 4 Zn 2+ OH - 4 Cu 2+ NH 3 4 Co 2+ Cl _ 4
  • 20.
    • Decomposition of complex by acid-base neutralization
      • Complexes containing NH 3 can be broken down by acid base decomposition by adding an acid
      • Ex. [Cu(NH 3 ) 4 ] 2+ + H + -> Cu 2+ + NH 4 +
        • The NH 3 acts as a base (accepts H + ions to form NH 4 + ). The rest of the complex is broken down.
    • Go over sheet from the “Ultimate Chemical Equation Handbook.” Responsible for all the reactions listed in the transition metal section.