Which among the following electronic configurations belong to main group elements?
A. [Ne]3s¹ 

B. [Ar]3d³4s²
C. [Kr]4d¹⁰5s²5p⁵

D. [Ar]3d¹⁰4s¹
E. [Rn]5f⁰6d²7s²
Choose the correct answer from the option given below :

The correct answer is A and C only.

To determine which electronic configurations belong to main group elements, let us understand what main group elements are:
Main group elements (also known as representative elements) include elements belonging to the s-block and p-block of the periodic table. In these elements, the outermost s or p subshells are being filled, while the inner d or f subshells are either completely empty or completely filled and do not participate in typical valence activities.

Let us analyze each of the given electronic configurations:

A. [Ne]3s¹:
This configuration has its valence electron in the 3s subshell. Since the outermost electron enters the s-orbital, it belongs to the s-block (specifically, Group 1, Sodium). Therefore, this is a main group element.

B. [Ar]3d³4s²:
In this configuration, the d-subshell is partially filled (3d³). Elements with partially filled d-orbitals belong to the d-block and are classified as transition elements. Therefore, this is not a main group element.

C. [Kr]4d¹⁰5s²5p⁵:
Here, the 4d subshell is completely filled (4d¹⁰), and the valence electrons are filling the 5s and 5p subshells (5s²5p⁵). Since the outermost electrons are in s and p subshells, it belongs to the p-block (specifically, Group 17, Iodine). Therefore, this is a main group element.

D. [Ar]3d¹⁰4s¹:
This configuration represents Copper (Cu). Although the 3d subshell is filled, it is a d-block transition element with characteristic transition element properties. Thus, it is not considered a main group element.

E. [Rn]5f⁰6d²7s²:
This configuration represents Thorium (Th), which is an actinoid (f-block/d-block transition series). Since it has electrons entering the d/f transition series orbitals, it is not a main group element.

Comparing our findings, only configurations A and C represent main group elements.