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The lanthanide contraction is the greater-than-expected decrease in atomic radii and ionic radii of the elements in the lanthanide series, from left to right. It is caused by the poor shielding effect of nuclear charge by the 4f electrons along with the expected periodic trend of increasing electronegativity and nuclear charge on moving from left to right.
The lanthanide contraction only partially accounts for this anomaly. [11] Because the 6s 2 orbital is contracted by relativistic effects and may therefore only weakly contribute to any chemical bonding, Hg–Hg bonding must be mostly the result of van der Waals forces. [11] [13] [14] Mercury gas is mostly monatomic, Hg(g).
Also, their relativistic effects are similar: The expected expansion of atomic radii from period 5 to 6 is almost exactly canceled out by the lanthanide contraction. Hafnium changes from its alpha form, a hexagonal close-packed lattice, to its beta form, a body-centered cubic lattice, at 2,388 K (2,115 °C; 3,839 °F). [43]
The lanthanide contraction, i.e. the reduction in size of the Ln 3+ ion from La 3+ (103 pm) to Lu 3+ (86.1 pm), is often explained by the poor shielding of the 5s and 5p electrons by the 4f electrons. [18] Lanthanide oxides: clockwise from top center: praseodymium, cerium, lanthanum, neodymium, samarium and gadolinium.
Due to the effects of the lanthanide contraction, yttrium and lutetium are very similar in properties. Yttrium and lutetium have essentially the chemistry of the heavy lanthanides, but scandium shows several differences due to its small size. This is a similar pattern to those of the early transition metal groups, where the lightest element is ...
The wider the electron shells are in space, the weaker is the electric interaction between the electrons and the nucleus due to screening. Further, because of differences in orbital penetration, we can order the screening strength, S, that electrons in a given orbital (s, p, d, or f) provide to the rest of the electrons thusly: > > > ().
The effect of the lanthanide contraction can be observed in the REE behaviour both in a CHARAC-type geochemical system (CHArge-and-RAdius-Controlled [40]) where elements with similar charge and radius should show coherent geochemical behaviour, and in non-CHARAC systems, such as aqueous solutions, where the electron structure is also an ...
Note the general increase in the residence time from vanadium to nickel, which mirrors the decrease in ion size with increasing atomic number, which is a general trend in the periodic table, though given a specific name only in the case of the lanthanide contraction. The effects of crystal field stabilization energy are superimposed on the ...