Melting and Boiling Points – d-Block Elements

The melting point and boiling point are attributes of a compound that define the involvement of the number of electrons from (n-1)d. These points also show the electrons participating in interatomic metallic bonds. When more electrons are added in the metallic lattice, the metallic bonds become stronger. Due to this strong bond, d-block elements have high melting and boiling points. When any group of elements are melted, metallic bonds between the atoms become weak. This way, the atoms present in the bond can move freely, and the bond breaks completely when the boiling point reaches its peak. The high melting and boiling points also indicate the strong forces of attraction between the elements of d-block. Besides metallic bonds, d-block elements also form covalent bonds with other elements.

Transition Elements 

Transition elements are characterised as partially filled d-orbitals in their atoms or simple ions. The f-block elements are also known as inner transition metals, including lanthanides and actinides. 

Transition metal compounds linked to zinc, cadmium, or mercury have been known for a long time. However, it was not until the late 1960s that widely applicable synthetic procedures were developed to establish bonds between group 12 elements and transition metals.

Properties of D-Block Elements

• d-block elements have higher densities than s-block metals (groups I and II).
• d-block elements form paramagnetic compounds, i.e., they are only slightly attracted to a magnetic field. 
• d-block elements have the characteristic properties of metals, such as malleability, hardness, lustre, etc. 

High Melting and Boiling Points

In d-block, all the elements have a high melting point, typically above 9000 C, in their solid state. There are some exceptions to this rule, such as zinc, cadmium, and mercury. The high melting and boiling points of d-block elements are generally based on how strong the metallic bond is between their atoms.

In any molecule, a metallic bond contains a higher number of unpaired electrons. Therefore, the metallic bond present is stronger, and the melting or boiling point is higher.

When we move from left to right in the periodic table in a transition series, the number of unpaired electrons increases up to configuration d5. Therefore, the strength of metallic bonds in d-block increases, along with the melting point.

By taking the first transition series into account, we can conclude that the melting point increases from Sc to Cr. Then, Mn shows a low melting point, which breaks the series of events. This is because the metallic bond is weak in comparison to the bond of other d-block elements. The 3d electrons do not participate in metallic bonding.

As we proceed further, the melting points decrease due to the decrease in the number of unpaired electrons. Metals that are present in the second and third transition series have greater enthalpies of atomisation compared to elements in the first transition series. Enthalpy of atomisation refers to the amount of change when a bond breaks.

Also, metals of the 2nd and 3rd transition series have comparatively higher melting points than the interrelated elements of the first transition series.

Conclusion 

The physical properties of the d-block elements set them apart from other elements due to their distinct configurations. However, their chemical properties can only be differentiated by experimenting to chemically change the substance.

Copper is a well known d-block element that has a low melting and boiling point in comparison to other elements because it has a fewer number of unpaired electrons. Zinc has the lowest melting and boiling point in the 3d series because it does not contain any d-electrons.