//M0//QN1//CS//DL0

Lanthanoid elements are classified by their 4f energy levels. They are extremely similar in properties. As the atomic number increases, the atomic and ionic radii decrease due to lanthanoid contraction from lanthanum to lutetium, and basicity also decreases. The sum of the three ionization enthalpies for each element is low, resulting in a predominant

+3 oxidation state. Ln3+ dominates the chemistry of these elements. Ln2+ and Ln4+ ions are always less stable than Ln3+. Inner orbital 4f electrons do not participate in bonding; they are neither removed nor significantly contribute to crystal field stabilization in complexes.(a) Which of the following is the most basic?

//M0//QN2//CS//DL0//EQ

All transition elements are metals and are therefore good conductors of electricity and heat. The melting and boiling points of transition elements are generally very high. Most transition elements melt above 1000°C, with a few exceptions. Transition metals have high enthalpy of atomization, which increases with an increase in the number of d- electrons and then decreases. This behaviour can also be explained based on increasing interatomic interactions with the increasing number of electrons.(a) Among the first transition series (atomic numbers 21 to 30), which element has the lowest enthalpy of atomization?

//X

(a) (D) Zn

Zinc (Zn) has an electronic configuration of [Ar]3d104s2. Since all its d-orbitals are completely filled, there are no unpaired d-electrons to participate in metallic bonding.

(b) (B) 3d5

μ = , where n is the number of unpaired electrons.

3d5: 5 unpaired electrons (n)

μ =

μ ≈ 5.92 BM

(c) (B) Less than alkali metals

Due to the presence of d-electrons and stronger effective nuclear charge, transition metals generally show less metallic character than alkali metals.

(d) (C) Fe, Co, Ni

In a transition series, the atomic radius initially decreases but then becomes almost constant in the middle of the series. For the elements Fe, Co, and Ni, the increasing nuclear charge is almost perfectly balanced by the increasing screening effect of the
d-electrons.

//M0//QN3//CS//DL0

A metallurgical research institute is developing high strength alloy material for aircraft engines. For this purpose, they search transition metals such as Cr, Mn, Fe, Co, Ni and their ions. During analysis they observe:

//X

//M0//QN4//CS//DL0//EQ

A company producing permanent magnets studies the magnetics behavior of transition metals. They analyze ions of Fe, Co, Ni and Cu to understand which metal ions have:

= = BM

Which metal ion is the most paramagnetic and

why?(c) Why do transition metals form strong metallic bond?(d) Explain why Cu2+ is coloured but Cu+ is colourless.

//X

(a) Fe2+ → 3d 6 → 4 unpaired e–

µ = = = 4.90 BM

Co2+ → 3d 7 → 3 unpaired e–

µ = = = 3.87 BM

Ni2+ → 3d 8 → 2 unpaired e–

µ = = = 2.83 BM

Cu2+ → 3d 9 → 1 unpaired e–

µ = = = 1.73 BM

(b) Fe2+ is most paramagnetic because of 4 unpaired electrons.

(c) Due to presence of delocalized d-electrons, giving : High cohesive energy, strong metallic bonding, high melting point.

(d) Cu2+ (d 9) → has one unpaired electron → d - d transitions → coloured.

//M0//QN5//CS//DL0//EQ

Cu+ (d 10) → No unpaired electron → No d - d transition → colourless.

Paramagnetism: Magnetic behaviour due to unpaired electrons; measured using spin only formula .

//X