[mistche20]

As far as I know: lanthanides have veery contracted 4f orbitals which means they are not involved in covalent bonding at all. But, I've been told that as Z increases, the polarizing power of Ln increases too, hence leading to a more "covalent" bonding with ligands, though it's still ionic, just a little more covalent. (fajans rules)

But, what I'm thinking is: okay, makes sense, but still, as Z increases, f orbitals become more contracted so technically less covalent bonding there should be right?? it's like two opposite effects only that to me they both make sense!!!

any ideas??