The d-block of the periodic table lies from group-3 to group-12. There are mainly three series transition metals, 3d series(Sc to Zn), 4d series(Y to Cd) and 5d series (La to Hg, omitting Ce to Lu).  

The d-block occupies the larger middle section flanked by s-block and p-block. Electronic Configuration is defined as the distribution of electrons of atoms or molecules in an atomic or molecular orbital. Electronic Configuration is represented by 2(n2) where n is the shell number.

Electronic configurations 

Electronic configurations are the summary of where the electrons are around the nucleus. The electronic configuration of an atom in a shell atomic model may be expressed by indicating the number of electrons beginning with first. The electronic configuration of an atom in the quantum mechanical model is stated by listening to the occupied orbitals, in order of filling, with the number of electrons in each orbital indicated by superscript. The electronic configuration of d-block elements is represented by (n-1) (d0-10) n(s1-2). d- block elements can find stability in half-filled orbital or completely filled full orbital.

Properties of d-block elements: 

The general properties of d-block elements are:

• Nearly all the transition elements have typical metallic properties such as high tensile strength, ductility, malleability, other thermal and electrical conductivity and metallic lustre.
• Except for mercury, which is liquid at room temperature, other transition elements have a typical metallic structure.
• The transition elements have very high densities as compared to the metal of group I and II(s-block).
• d- block elements form compounds that are generally paramagnetic in nature.
• d- block elements are used to make alloys with other metals.
• d- blocks elements have a large size; that’s why they form interstitial compounds with elements such as hydrogen, boron, carbon, nitrogen, etc.
• Most of the transition metals such as Mn, Ni, Co, Cr, V, etc., and their compounds have been used as catalysts.

Electronic configuration of d-block elements:

The transition elements consist of 4 rows of 10 elements. These rows are called first, second, third and fourth transition series which involve filling of 3d, 4d, 5d and 6d orbitals respectively.

First Transition Series:

The first transition series elements start from Scandium, Sc (Z= 21) to Zinc, Zn (Z = 30). 

Second transition series 

The second transition series consists of elements from yttrium, Y (Z=39) to cadmium, Cd (Z=48).  

Third transition series

This series consists of elements of lanthanum (Z=57) and all the elements from hafnium (Z=72)  to mercury (Z=80). This series involves the filling of 5d orbitals.

Fourth transition series

It involves the filling of 6d-subshells starting from actinium (Z=89). It includes elements with atomic number 104 onwards.

Electronic configuration of iron

Electronic configuration of iron is [Ar]3d64s2 . Iron has an atomic number of 26  which means the number of electrons present in iron is 26 and it belongs to group eight of the periodic table. Iron is also known as the second most abundant metal which is present in the crust of the earth. The electronic configuration of iron is1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2.

Conclusion 

Electronic configuration of the d block is divided into four series and the d block lies from group-3 to group-12 of the periodic table. The electronic configuration of elements makes the study of electrons easy and understandable for the students. The d block elements have high melting and boiling point and also form coloured compounds with other elements of the periodic table. Configuration of iron plays an important role in the study of iron. In the end, we conclude that electronic configuration is a very important aspect of the periodic table as it makes the study and discovery of new elements easy.