Question

Which one of the following statements concerning lanthanides elements is false?

• A. Most characteristic oxidation state of lanthanides elements is +3
• B. All lanthanides are metals
• C. The ionic radii of trivalent lanthanide steadily increase with increase in atomic number
• D. Lanthanides are separated from one another by ion exchange methods

Answer 1

Answer: (C)

Lanthanoids The series involving the filling of $4 f$-orbitals following lanthanum $La(Z=57)$ is called lanthanoid series. The elements present in the series are called lanthanoids. Some general characteristics of lanthanoids are following
(a) All lanthanoids exhibit a common stable oxidation state.
(b) The steady decrease in atomic and ionic sizes of lanthanide elements with increasing atomic number is called lanthanoid contraction. The ionic radii decreases from $Ce ^{3+}$ to $Lu ^{3+}$ ions.
(c) All the lanthanoids are silvery white soft metals.
(d) Lanthanoids are chemically similar. It is difficult to separate them by chemical reaction. They are separated by ion exchange methods.