d-Block elements- Introduction

“The elements in which the last differentiating electron enters into the d-orbitals of the penultimate shell i.e. (n–1) d where n is the last shell is called d-block elements”. A transition element may also be defined as the element which partially filled d-orbital in their ground state or most stable oxidation state.

The properties of these elements are intermediate between the properties of s-block and p-block elements. These elements represent a change or transition in properties from more electropositive elements (s-block) to less electropositive elements (p-block). Therefore, these elements are called transition elements.

Position in the periodic table:

The position of the d-block element has been shown in periodic table as follows:

d-block elements lie in between ‘s’ and ‘p’ block elements, i.e. these elements are located in the middle of the periodic table.
d-block elements are present in:

4^th period (₂₁Sc to ₃₀Zn, 10 elements) 1st Transition series.
5^th period (₃₉Y to ₄₈Cd, 10 elements) 2nd Transition series.
6^th period (₅₁La, ₇₂Hf to ₈₀Hg, 10 elements) 3rd Transition series.
7^th period (₈₉Ac, ₁₀₄Rf to ₁₁₂Uub, 10 elements) 4th Transition series

Thus, the electronic configuration of chromium (Z = 24) and copper (Z = 29) are 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹ and 1s² 2s² 2p⁶ 3s⁶ 3p⁶ 3d¹⁰ 4s¹ respectively.

Electronic Configuration of the d-Block Elements:

The general electronic configuration of d-block elements is (n −1)d^1─10 ns^1─2, where (n −1) stands for the inner d orbitals.
In d-block, each horizontal row consists of ten elements as d-subshell can accommodate a maximum of 10 electrons.
Depending upon the d-orbitals of which penultimate shell i.e. n = 4, 5, 6, 7 are filled, four rows (called series) or ten elements each obtained. They correspond to 3d, 4d, 5d and 6d subshells
Energy of ‘(n–1)d’ subshell is slightly greater than ‘ns’ subshell, hence orbital is filled first then (n – 1) d orbitals.
The general electronic configuration of d-block/d-series elements be shown as follows: