24.1 d-block elements

• d-block elements have their highest energy electron in a d sub-shell
• Chromium atoms have a half-filled d sub-shell because it has extra stability
• Copper atoms have a fully filled d sub-shell
• 4s electrons are lost before the 3d electrons
• Transition elements are d-block elements that form an ion with an incomplete d sub-shell
• Scandium and zinc are not classified as transition elements because they do not form ions with a partially filled d-orbital
• Properties of transition elements

  • form compounds with different oxidation states
  • form coloured compounds
  • act as catalysts
• A catalyst increases the rate of a chemical reaction by providing an alternative reaction pathway with a lower activation energy