Transition metals (A-level only) common mistakes

Common mistakes

• Confusing transition metals with main group elements

  Students often confuse transition metals with main group elements due to similarities in properties.

  Fix itRemember that transition metals are defined by their ability to form ions with incomplete d subshells, while main group elements do not have this characteristic.

• Confusing oxidation states with charges

  Students often confuse the oxidation state of an element with the overall charge of a compound.

  Fix itRemember that oxidation states refer to individual elements, while the charge refers to the entire compound.

• Confusing absorption with reflection

  Students often confuse the concept of absorption of light with reflection when explaining why transition metals are coloured.

  Fix itRemember that transition metals absorb specific wavelengths of light, and the colour observed is the complementary colour of the absorbed light.

• Confusing oxidation states with oxidation numbers

  Students often use the terms interchangeably, leading to incorrect interpretations of redox reactions.

  Fix itRemember that oxidation states refer to the actual charge of an atom in a compound, while oxidation numbers are a bookkeeping tool that may not reflect real charges.

• Confusing ligands with metal ions

  Students often confuse the roles of ligands and metal ions in complex formation.

  Fix itRemember that ligands donate electron pairs to metal ions, which are the central atoms in complex ions.

• Confusing coordination number with oxidation state

  Students often confuse the coordination number with the oxidation state of the metal ion.

  Fix itRemember that the coordination number refers to the number of bonds formed with ligands, while the oxidation state indicates the charge of the metal ion.

• Confusing Tetrahedral and Square Planar Complexes

  Students often confuse the geometries of tetrahedral and square planar complexes.

  Fix itRemember that tetrahedral complexes have four ligands with bond angles of approximately 109.5°, while square planar complexes have four ligands with bond angles of 90°.

• Confusing ligand types

  Students often confuse bidentate and monodentate ligands.

  Fix itRemember that bidentate ligands can attach to the metal at two points, while monodentate ligands attach at one point.

• Incorrectly balancing ligand substitution equations

  Students often forget to balance the number of ligands on both sides of the equation.

  Fix itAlways ensure that the number of ligands and metal ions is balanced in the final equation.

• Confusing cis-trans and optical isomerism

  Students often mix up the definitions and characteristics of cis-trans isomerism with optical isomerism.

  Fix itRemember that cis-trans isomerism involves the arrangement of ligands in space around a metal center, while optical isomerism involves non-superimposable mirror images.