Question

2. Are Pr(ll), Fe(lll), and Ca(ll) hard or soft Lewis acids? Explain. What are their respective ionic radii in octahedral complexes?

Answer 1

Hard lewis acids have high positive charge density, high polarising power, without any d electron or few d electron or f electrons.

lanthanide elements.

Pr (II) is 4f³ system. it has few f electrons, hence it is hard lewis acid.

Fe (III) is d⁵ system , so it has less d electrons, it is hard lewis acid

Ca (II) has no d electron, it is also a hard lewis acid.

Ionic radii of octahedral complexes of Pr(II) , Fe (III) and Ca (II) decreses in case of strong field ligand.

Ionic radii of Pr (II) in octahedral complex is = 114 pm

Ionic radii of Fe (III) in octahedral complex is = high spin =78.5 pm, low spin- 69pm

Ionic radii of Ca (II) in octahedral complex is = 114pm