NEET 2024 Physics Question 25 Solution

An isolated neutral atom of atomic number Z contains exactly Z positively charged protons in its nucleus (charge +Ze) and Z negatively charged extranuclear electrons (charge -Ze). The algebraic sum of charges is zero:

In the opening section of NCERT Physics, the textbook introduces atomic models by noting that ordinary matter is stable and that atoms of each chemical element emit a unique, characteristic line emission spectrum when energized. Under this textbook definition, Statement II is treated as correct, leading to Option (3): "Both Statement I and Statement II are correct".

Following the examination, subject matter experts and candidates formally challenged Statement II on two solid physical grounds: 1. Not all atoms are stable: elements with Z > 82 (e.g., Uranium, Polonium, Radium) as well as radioactive isotopes of lighter elements (e.g., Carbon-14, Tritium) undergo spontaneous nuclear decay and are inherently unstable. 2. Atoms in their ground state are stable but do NOT emit radiation; emission occurs only when atoms transition downward from excited states. Under this scientific rigor, Statement II is incorrect, leading to Option (1): "Statement I is correct but Statement II is incorrect".

After expert committee review, the National Testing Agency (NTA) officially upheld both perspectives and awarded full credit for BOTH Option (1) and Option (3) in the NEET 2024 Final Answer Key.