Question

Which is the strongest base among the following?
(A) La(OH)₃
(B) Lu(OH)₃
(C) Ce(OH)₃
(D) Yb(OH)₃

Answer 1

Hint :Lanthanides are a group of 15 chemical elements whose atomic numbers range from 57 to 71. In the 5d shell, each of these elements has one valence electron. The elements have properties in common with the group's first member, lanthanum. Lanthanides are silver-colored metals that are reactive.

Complete Step By Step Answer:
Lanthanide contraction is the gradual reduction in the size of the atoms and ions of the rare earth elements from lanthanum (Z = 57) to lutetium (Z = 71) as the atomic number increases. The nuclear charge increases by one unit with each successive atom, followed by a similar increase in the number of electrons present in the 4f orbitals surrounding the nucleus. The 4f electrons imperfectly protect each other from the augmented positive charge of the nucleus, resulting in a steady rise in the effective nuclear charge attracting each electron as the lanthanide elements progress, resulting in successive decreases in atomic and ionic radii.
All of the lanthanides combine to form Ln(OH)₃ hydroxides. They are both ionic and simple in nature.
The scale of the tripositive lanthanide ion M³⁺ decreases with increasing atomic number, i.e., from La³⁺ to Lu³⁺, due to lanthanoid contraction. It causes the basic character to drop from La³⁺ to Lu³⁺. The covalent character of the M-OH bond steadily increases as the ionic character of the M-OH bond decreases. As a result, the resulting hydroxides' fundamental strength falls from La(OH)₃ to Lu(OH)₃. As a result, La(OH)₃ is the most strong.

Note :
A change in the attraction forces on the electrons in the atom causes the shielding effect, which is characterised as a reduction in the effective nuclear charge on the electron cloud. It's a kind of electric-field screening that's a little different. This influence is also important in a number of material science ventures.