Formation of Coloured Ions by D Block Elements

The elements of groups 3-12 are found in the d-block of the periodic table, where the d orbitals are gradually filled throughout each of the four long periods. 

The d–block is flanked by the s– and p–blocks in the middle section of the periodic table. Because of their position between s– and p– block elements, the elements of the d-block are given the label ‘transition.’ The transition metals’ three rows, 3d, 4d, and 5d, are formed when the d–orbitals of the penultimate energy level in their atoms absorb electrons. The sixth row of 6d is still incomplete.

General Properties of d block element

Almost all transition elements (d block elements) have metallic qualities such as high tensile strength, flexibility, malleability, high thermal and electrical conductivity, and metallic lustre. They exhibit one or more conventional metallic structures at normal temperatures, except for Zn, Cd, Hg, and Mn.

Except for Zn, Cd, and Hg, the transition metals are extremely hard and have limited volatility. They have high melting and boiling points.

The involvement of a greater number of electrons from (n-1)d in addition to the ns electrons in interatomic metallic bonding is attributed to the high melting temperatures of these metals.

Formation of Coloured Ions by D Block Elements

The energy of excitation corresponds to the frequency of light absorbed when an electron from a lower energy d orbital is excited to a higher energy d orbital. This frequency is usually in the visible range. The colour seen matches the light absorbed complementary colour. The type of ligand determines the frequency of the light absorbed.

Let’s look at some examples:

Catalytic Properties

The catalytic activity of transition metals and related derivatives is well recognised. Their ability to adopt multiple oxidation states and form complexes is credited with this action.

Some examples are vanadium (V) oxide (in the Contact Process), finely divided iron (in Haber’s Process), and nickel (in Catalytic Hydrogenation). Catalysts on a solid surface include the production of bonds between reactant molecules and atoms on the catalyst’s surface (bonding is done with 3d and 4s electrons in the first-row transition metals). It increases the concentration of reactants on the catalyst surface while simultaneously weakening the links between the interacting molecules (the activation energy is lowering).

Transition metal ions are also more effective as catalysts because they can change their oxidation states.

Alloy Formation

An alloy is a metal mixture made by combining its constituents.

Alloys are solid solutions in which the atoms of one metal are randomly dispersed among the atoms of the other. These alloys are made up of atoms with metallic radii within 15% of one another. Transition metals easily create alloys due to their comparable radii and other properties. The resulting alloys are hard and frequently have high melting points. Ferrous alloys are the most well-known: chromium, vanadium, tungsten, molybdenum, and manganese are used to make a variety of steels and stainless steels.

Transition metal alloys with non-transition metals, such as brass (copper-zinc) and bronze (copper-tin), are also very important in the metal industry.

Conclusion

The d-block, which includes Groups 3-12, takes up most of the middle region of the periodic table.

The inner d orbitals of these elements are gradually filled. The f-block is located near the bottom of the periodic table, and the 4f and 5f orbitals are gradually filled in the elements of this block.

The formation of coloured ions by D block elements is due to one or more unpaired electrons common in transition metal ions. When visible light strikes a transition metal complex or ion, the unpaired electrons in the lower energy d-orbitals are promoted to higher energy d-orbitals, a process known as the d-d transition. Because the energy involved in the d-d transition is quantised, only a specific wavelength is absorbed, while the rest of the visible spectrum is transmitted. As a result, transmitted light has a complementary colour to the absorbed colour.