Question

Which among the following electronic configurations belong to main group elements?

• A. B and E only
• B. A and C only
• C. D and E only
• D. A, C and D only

Answer 1

Answer: (B)

(2)

Answer 2

Main group elements are those elements in which the last electron enters an s or a p subshell. These include elements of the s-block (Groups 1 and 2) and the p-block (Groups 13 to 18). Elements where the last electron enters a d subshell (d-block, Groups 3 to 12) are called transition elements, and those where the last electron enters an f subshell (f-block, Lanthanides and Actinides) are called inner transition elements.

Let's analyze each given electronic configuration:

A. [Ne]3s¹

• The outermost electron is in the 3s subshell. This corresponds to an s-block element (specifically, Sodium, Na, in Group 1).
• Therefore, A is a main group element.

B. [Ar]3d³4s²

• The differentiating electron (last added electron) is in the 3d subshell. This corresponds to a d-block element (specifically, Vanadium, V, in Group 5).
• Therefore, B is not a main group element; it is a transition element.

C. [Kr]4d¹⁰5s²5p⁵

• The outermost electrons are in the 5s and 5p subshells, with the last electron entering the 5p subshell. This corresponds to a p-block element (specifically, Iodine, I, in Group 17). The filled 4d¹⁰ subshell does not change its classification as a p-block element.
• Therefore, C is a main group element.

D. [Ar]3d¹⁰4s¹

• The differentiating electron is in the 3d subshell (even though the 4s subshell is the outermost). This corresponds to a d-block element (specifically, Copper, Cu, in Group 11).
• Therefore, D is not a main group element; it is a transition element.

E. [Rn]5f⁰6d²7s²

• The differentiating electron is in the 6d subshell. This corresponds to a d-block element (specifically, Rutherfordium, Rf, in Group 4).
• Therefore, E is not a main group element; it is a transition element.

Based on the analysis, only configurations A and C belong to main group elements.