Question

Among the 3d-block elements, show exception with respect to their electronic configuration.

• A. Mn and Ni
• B. Mn and Fe
• C. Fe and Zn
• D. Cr and Cu

Answer 1

The correct option is D Cr and Cu

3d-block elements belong to 4th period in the modern periodic table. It consists of elements from scandium (Sc) to zinc (Zn).

Among 3d-block elements, chromium (Cr) and copper (Cu) show exceptional electronic configuration due to the stability of half filled electronic configurations. The expected and actual electronic configuration for Cr and Cu are given below:
$$\begin{array}{ccc}\text{Element}& \text{Expected}& \text{Actual}\\ \text{Cr}& {\text{[Ar]4s}}^2{\text{3d}}^4& {\text{[Ar]4s}}^1{\text{3d}}^5\\ \text{Cu}& {\text{[Ar]4s}}^2{\text{3d}}^9& {\text{[Ar]4s}}^1{\text{3d}}^{10}\end{array}$$