JEE Main Chemistry Question (2026) — Solution

Step-by-step solution

Species with the same number of valence electrons and the same skeletal structure generally have similar Lewis dot structures (isoelectronic species). For pair A: SO _3^ 2- has 6 + 3(6) + 2 = 26 valence electrons. CO _3^ 2- has 4 + 3(6) + 2 = 24 valence electrons. Since they have different numbers of valence electrons, they do not have similar Lewis dot structures ( SO _3^ 2- has a lone pair on the central atom and is pyramidal, while CO _3^ 2- has no lone pair on the central atom and is trigonal planar). For pair B: O _2^ 2- has 2(6) + 2 = 14 valence electrons. F _2 has 2(7) = 14 valence electrons. Both have a single bond and three lone pairs on each atom, so they have similar Lewis dot structures. For pair C: CN ^- has 4 + 5 + 1 = 10 valence electrons. CO has 4 + 6 = 10 valence electrons. Both have a triple bond and one lone pair on each atom, so they have similar Lewis dot structures. For pair D: NH _3 has 5 + 3(1) = 8 valence electrons. H _3 O ^+ has 6 + 3(1) - 1 = 8 valence electrons. Both have three single bonds and one lone pair on the central atom, so they have similar Lewis dot structures. For pair E: MnO _4^ 2- has 7 + 4(6) + 2 = 33 valence electrons. CrO _4^ 2- has 6 + 4(6) + 2 = 32 valence electrons. Since they have different numbers of valence electrons ( MnO _4^ 2- has an unpaired electron), they do not have similar Lewis dot structures. Thus, pairs A and E do not have similar Lewis dot structures. Answer: A and E