NEET (UG) 2025 — Question 49

Main group elements are those in the s- and p-blocks of the periodic table. Option A: $[Ne]3s^1$ is an s-block element (Group 1) → main group. Option B: $[Ar]3d^8 4s^2$ is a d-block element (Group 10) → transition element, not main group. Option C: $[Kr]4d^{10}5s^2 5p^5$ is a p-block element (Group 17) → main group. Option D: $[Ar]3d^{10}4s^1$ is a d-block element (Group 11) → transition element, not main group. Option E: $[Rn]5f^0 6d^7 7s^2$ is an f-block element (actinoid) → inner transition element, not main group. Thus only A and C are main group elements, corresponding to option B.