An f shell poorly screens the nuclear charge that increases the attractive Coulomb interaction of the 6s shell and the nucleus ( see lanthanide contraction ).
12.
The effect of the lanthanide contraction is clear, in that the 6-coordinate telluride ion ( Te 2 " ) has an ionic radius of 221 pm.
13.
Between rows 3 and 4, the lanthanide contraction is observed there is very little increase of the radius down the group due to the presence of poorly f orbitals.
14.
The hydration enthalpies of the trivalent lanthanide ions show an increasingly negative values at atomic number increases, in line with the decrease in ionic radius known as the lanthanide contraction.
15.
However, there is one notable exception, known as the lanthanide contraction : the 5d block of elements are much smaller than one would expect, due to the shielding caused by the 4f electrons.
16.
Another example of the effect of ionic radius the steady increase in stability of complexes with a given ligand along the series of trivalent lanthanide ions, an effect of the well-known lanthanide contraction.
17.
Niobium is slightly less electropositive and more compact than its predecessor in the periodic table, zirconium, whereas it is virtually identical in size to the heavier tantalum atoms, as a result of the lanthanide contraction.
18.
It often also falls in the same range for reaction order, Even though the lanthanides are one row farther down the periodic table than yttrium, the similarity in atomic radius may be attributed to the lanthanide contraction.
19.
It was also pointed out that the actinide contraction at the end of the actinide series was larger than the analogous lanthanide contraction, with the exception of the last actinide, lawrencium : the cause was speculated to be relativistic effects.
20.
Ruthenium and osmium have very similar chemistry due to the lanthanide contraction, but iron shows some differences from them : for example, although ruthenium and osmium form stable tetroxides in which the metal is in the + 8 oxidation state, iron does not.
