Lanthanum and Actinium should be placed in d block
Placing lanthanum (La), actinium (Ac), lutetium (Lu), and
lawrencium (Lr) all in the f-block is not suitable for the reasons discussed here and for the additional reason that the f-block would then
have 15 groups when it should have 14 groups. It should be noted that
the periodic table adopted by the IUPAC (18) and the physics laboratory of the NIST (19) do place lanthanum (La) and actinium (Ac)
below yttrium (Y) in group 3 (IIIB).