Transition Metals and Periodic Trends Quiz

Transition Metals

• The Aufbau principle is not always obeyed, especially for transition metals
• The first row (3d block) transition metals generally fill the 4s orbital before the 3d orbitals, but there are exceptions - Cr and Cu are the most notable examples
• The second row (4d block) metals suggest the 4d orbital fills first before 5s
• It is difficult to predict the electronic configurations of transition metal ions in the gas phase
• It is easier to predict the electronic configuration of ions in coordination complexes
• In coordination complexes, the energy gap between the 3d and 4s orbitals is larger than in the gas phase
• The electronic configuration of transition metals in coordination complexes is focused on the electrons in the d-orbitals

Periodic Trends

• Transition metals have relatively constant atomic size across a row because of the increasing effective nuclear charge (Zeff) due to the addition of protons
• Shielding ability of electrons decrease as the orbital shape changes: s>p>d>f
• The third row of transition metals have filled f-subshells (orbitals), causing poor shielding by f-orbitals and a smaller atomic size compared to the second row - lanthanoid contraction

Transition Metal Oxidation States

• Transition metals can have multiple oxidation states because of their d electrons, which are readily available for bonding
• For example, Vanadium (V) can exist as V0, V+1, V+2, V+3, V+4, V+5, etc.
• Common transition metals and their oxidation states include:
  • Sc: +3
  • Ti: +2, +3, +4
  • V: +2, +3, +4, +5
  • Cr: +2, +3, +6
  • Mn: +2, +3, +4, +6, +7
  • Fe: +2, +3
  • Co: +2, +3
  • Ni: +2, +3
  • Cu: +1, +2
  • Zn: +2
• The oxidation state of a transition metal can be determined by analyzing the charges on other atoms in the compound, for example, by considering whether the atoms are cations or anions

Coordination Complexes

• Coordination complexes are formed when a metal ion binds to ligands, which are molecules or ions that donate a pair of electrons to the metal ion
• The number of ligands that bind to the metal ion is called the coordination number
• Coordination complexes can have various shapes and sizes, depending on the metals and ligands
• The colour of coordination complexes can vary depending on the metal and the ligands. This is due to the absorption of light by electrons in the d-orbitals of the metal

Additional Notes

• The text references several activities with specific instructions
• The text highlights “naked/free” and “dressed” atoms. Naked atoms are in the gas phase, while dressed atoms are in coordination complexes
• The text recommends referring to external resources for information on transition metal uses
• The text refers to a demonstration involving the reaction of VO3 and Zn, where the color changes due to the different oxidation states of Vanadium