Transition metals

• The d-block elements are located between Group 2 and Group 13 of the periodic table
• Across the periodic table from scandium to zinc, the 3d sub-shell has the highest energy and electrons are added to 3d orbitals - hence the name d-block elements.
• The d-block elements are all metallic, displaying the typical physical properties of metals

  • high melting points and boiling points
  • shiny
  • conduct electricity and heat
• atoms of the d-block fill their 4s sub-shell before they fill their 3d sub-shell
• Electron configuration endings of

  • Sc = 3d1 4s2
  • Ti = 3d2 4s2
  • V = 3d3 4s2
  • Cr = 3d5 4s1
  • Mn = 3d5 4s2
• Electron configuration endings of

  • Fe = 3d6 4s2
  • Co = 3d7 4s2
  • Ni = 3d8 4s2
  • Cu = 3d10 4s1
  • Zn = 3d10 4s2
• The electron configurations of chromium and copper

  • do not follow the expected principle for placing electrons singly in orbitals before pairing
  • a simplistic explanation is one of stability
  • it's believed that a half-filled d5 sub-shell and a fully filled d10 sub-shell give additional stability to atoms of chromium and copper
• when forming an atom, the 4s orbital fills before the 3d orbitals
• when forming an ion, the 4s orbital empties before the 3d orbitals
• Fe atom: 1s2 2s2 2p6 3s2 3p6 3d6 4s2

  Fe2+ ion: 1s2 2s2 2p6 3s2 3p6 3d6 (Two 4s electrons lost)

  Fe3+ ion: 1s2 2s2 2p6 3s2 3p6 3d5 (Two 4s and one 3d electron lost)
• Transition elements are defined as d-block elements that form at least one ion with a partially filled d-orbital
• Scandium and zinc are d-block elements, but they do not form at least one ion with a partially filled d-orbital and are not classified as transition elements.
• The electron configuration of Sc is 1s2 2s2 2p6 3s2 3p6 3d1 4s2

  Sc3+ has an electronic configuration of 1s2 2s2 2p6 3s2 3p6
• Zn: 1s2 2s2 2p6 3s2 3p6 3d10 4s2

  Zn2+: 1s2 2s2 2p6 3s2 3p6 3d10
• Sc3+ ions have empty d-orbitals and Zn2+ ions have full d-orbitals. So scandium and zinc do not form ions with partially filled d-orbitals and are not therefore classified as transition elements.
• The transition elements have a number of characteristic properties that are different from other metals:

  • They form compounds in which the transition element has different oxidation states
  • They form coloured compounds
  • The elements and their compounds can act as catalysts
• What is required for a substance to absorb visible light?


  • There must be room for an electron in one orbital to be excited into another orbital
  • The difference between their energy levels must correspond to a frequency of visible light
• all transition metals except chromium and copper have full 4s subshells
• copper and zinc have full 3d subshells