Which Elements are d-block or f-block?

Most current Periodic tables have:

• La as first 5d transition element
• Ac as first 6d transition element

Reasons?

possibly erroneous (early) interpretation of atomic spectra Æ misleading electronic configurations?

Some ground state electronic configurations

Calcium [Ar]4s² Æ Scandium [Ar]4s²3d¹

Strontium [Kr]5s² Æ Yttrium [Kr]5s²4d¹

Barium [Xe]6s² Æ Lanthanum [Xe]6s²5d¹

Ytterbium [Xe]6s²4f¹⁴ Æ Lutetium [Xe]6s²4f¹⁴5d¹

Radium [Rn]7s² Æ Actinium [Rn]7s²6d¹

Nobelium [Rn]7s²5f¹⁴ Æ Lawrencium [Rn]7s²5f¹⁴6d¹

In each case: Differentiation by (n-1)d¹ ~ as expected for the start of a transition series

• Lutetium and Lawrencium are just as good candidates to be the first elements of the 3rd and 4th transition series as Lanthanum and Actinium

Some suggestions why Lu might best regarded as the first 5d transition element.

• Periodic Trends in Various Properties

 • Structures of Metal, Metal Sesquioxide (M₂O₃) and Metal Chloride (MCl₃)

Similarities for Sc, Y, Lu

Differences from La

Revised Medium-Block Format Periodic Table

See the article: W.B. Jensen, The Positions of Lanthanum(Actinium) and Lutetium(Lawrencium) in the Periodic Table, Journal of Chemical Education, 1982, 59, p. 634-636

Bibliography