Question

Which of the following statements concerning lanthanides elements is false?

• A. Lanthanides are separated from one another by ion-exchange method
• B. Ionic radii of trivalent lanthanides steadily increases with increase in the atomic number
• C. All lanthanides are highly dense metals
• D. More characteristic oxidation state of lanthanides elements is +3

Answer 1

The correct option is B Ionic radii of trivalent lanthanides steadily increases with increase in the atomic number

The chemistry of the lanthanides differs from main group elements and transition metals because of the nature of the 4f orbitals. These orbitals are "buried" inside the atom and are shielded from the atom's environment by the 4d and 5p electrons. As a consequence, the chemistry of the elements is largely determined by their size, which decreases gradually with increasing atomic number. This phenomenon is known as the lanthanide contraction. All the lanthanide elements exhibit the oxidation state +3.
Because of this lanthanide contraction, all lanthanide metals are highly dense.