Textbook 320-340

Ionization Energies

• Group 13 elements have lower ionization energies than group 2 because p orbitals are higher in energy and further from the nucleus, making it easier to remove an electron.

• Group 16 elements have a lower first ionization energy than group 15 because the p4 orbital has two electrons repelling each other, making it easy to remove one.

Transition Elements

• From K-Br, the atomic radii usually decrease.

• The small decrease in atomic radii is because of the 3d orbital that fills up, helping to shield the 4s orbital.

• Because the atomic radii of transition metals are so similar, they can form alloys, mixtures of different metals, since their structures are so similar.

• Zinc is not a transition metal

  • It doesn’t form colored compounds

  • It only exists in the 2+ oxidation state in compounds

  • It is this way because in Zn and Zn2+ it’s orbitals are always full, not reactive.

• Transition metals physical properties:

  • High electrical and thermal conductivity

  • High melting point

  • Malleable-Can be beaten into shape

  • High Tensile strength

  • Ductile-Can be drawn into wires

  • Ferromagnetic (Iron, Cobalt, and Nickel)

• These properties are explained by metallic bonding, which is possible because of the closeness in energy between 4s and 3d orbitals.

• Metallic bonding causes a sea of delocalized electrons, which makes the metals strong.

• Metals are dense because of their small atomic radii.

• Magnetic properties from metals come from them having unpaired electrons in their orbitals.

• Transition metals chemical properties:

  • Form compounds with more than one oxidation state

    • Transition metals have variable oxidation states because of the similarity between s and d orbitals.

    • All transition metals have 2+ and 3+ oxidation states

    • 3+ is stable from Sc to Cr, but after that 2+ is more common because of the high third ionization energy

    • The maximum oxidation state increases by +1 until manganese, with a max of+7, then decreases by -1 every one after that.

    • Ions above +3 have covalent character, since they polarize negative ions.

    • Ions with high oxidation states are often oxidizing agents.

  • Form a variety of complex ions

    • When transition metal ions are put in a solution, like water, they can form a complex ion.

    • The high charge density attracts water molecules and forms coordination bonds.

    • Complexes are formed when a central ion is surrounded by molecules that have only two electrons.

    • This forms a dative/coordinate bond, a covalent bond where the electrons share are supplied by one element.

      • Example: When an extra hydrogen bonds to NH3, the other electron is supplied by nitrogen only.

      • When iron 3+ is in a water solution, the ligands are formed by electrons supplied solely by the water molecules, H2O.

    • All the ligands or molecules on the outside, have at least one atom with only two electrons that bonds with the positive ion.

    • The number of bonds in the complex is called the coordination number.

    • When the metal is in a solution, the ligands cause the d sublevel to separate into two parts, 2 higher orbitals, and 3 lower ones. The 2 higher orbitals are in a higher energy level.

  • Form colored compounds

    • The color of transition metal ions is related to d orbitals, where full and empty orbitals make colorless compounds

      • 3d1-Violet

      • 3d2-Green

      • 3d3-Violet

      • 3d5-Pink

      • 3d5-Yellow

      • 3d6-Green

      • 3d7-Pink

      • 3d8-Green

      • 3d9-Blue

    • The color of a compound is affected by which color it absorbs and which color it reflects, which is the complementary, or opposite color. Coper Sulfate is turquoise since it absorbs orange light.

    • Transition metals absorb light because the d-sublevel splits into two

      • In the electric field produced by the ligand’s single pair of electrons, the orbitals split into two levels.

      • When light passes through a solution, on 3d electron is excited to a higher energy sublevel. A photon gets absorbed and the complementary light is transmitted.

      • When the solution has a greater charge density, the complex absorbs a shorter wavelength of color. This creates a greater division in the d orbitals.

      • The concentration of a substance affects the absorbance of light.

      • When you don’t know the concentration of a solution, you can use the wavelength it absorbs to find it. Make solutions of that substance with known concentrations, measure the absorbance of each solution, then interpolate the known absorbance to find the concentration of the substance.

  • Act as catalysts when elements or compounds

    • Catalysts: Substances that lower the activation energy of a reaction.

    • Iron is an example of a catalyst in the formation of ammonia, NH3