Which of the following is the least basic in nature-:
a) La(OH)3 b) Ce(OH)3 c) Yb(OH)3 d) Lu(OH)3
Answers
Answer:
La(OH)3 is most basic and Lu(OH)3 is least basic. Due to lanthanide contraction. As the size of lanthanide ions decreses from La3+ to Lu3+ , the covalent character of the hydroxides increases and hence the basic strength decreases.
Answer:
Lu(OH)₃ is the least basic.
Explanation:
As the size of the lanthanoid ions decreases from La³⁺ to Lu³⁺, the covalent character of the hydroxides increases and hence the basic strength decreases. Thus, La(OH)₃ is the most basic whereas Lu(OH)₃ is the least basic.
This is a consequence of Lanthanoid contraction. Lanthanoid contraction is the regular decrease in the atomic and ionic radii of lanthanoids with increasing atomic number.
Due to lanthanoid contraction, the basic strength of oxides and hydroxides of lanthanoids decreases with an increase in atomic number. The accumulating lanthanoid contraction goes on decreasing the size of lanthanoid cations. Therefore, with an increase in atomic number, the polarising power of lanthanoid cation increases. This results in a regular decrease in the ionic character of oxides and hydroxides and they become less and less basic.