Chapter 22, Problem 14PS

Interpretation Introduction

Interpretation:

The reason for atomic radii of the transition metals changes across the period with the change in electronic structure has to be explained.

Concept introduction:

$Lanthanoid$ Contraction or lanthanide contraction:

When increasing atomic number from lanthanum to lutetium the decrease in the size of the atoms and ions of the rare earth elements. The number of valence electron is increase in 4f orbitals from lanthanum to lutetium, the nuclear charge is more positive by one unit.

The 4f electrons very incorrectly shield each other from the increased positive charge of the nucleus, so that the effective nuclear charge attracting each electron steadily increases through the $lanthanoid$ elements, resulting in successive reductions of the atomic and ionic radii.

The lanthanum ion (${\text{La}}^{\text{3+}}$) to lutetium ion (${\text{Lu}}^{\text{3+}}$) there is a reductions of the atomic and ionic radii which cause there is contraction in the size, this called as lanthanide contraction.