Atoms & Nuclei

JEE Main level, single correct, medium

173 of 239

Question 173 of 239

Consider the following statements:
AA. Atoms of each element emit characteristics spectrum.
B.B. According to Bohr's Postulate, an electron in a hydrogen atom revolves in a certain stationary orbit.
C.C. The density of nuclear matter depends on the size of the nucleus.
D.D. A free neutron is stable but a free proton decay is possible.
E.E. Radioactivity is an indication of the instability of nuclei. Choose the correct answer from the options given below.

Show answer and solution

Answer: (B) A,BA,Band EE only.

(A)(A) True, an atom of each element emits a characteristic spectrum.
(B)(B) True, according to Bohr's postulates mvr=nh2πmvr=\dfrac{nh}{2\pi } and hence electron resides into orbits of specific radius called stationary orbits.
(C)(C) False, the density of the nucleus is constant.
(D)(D) False, A free neutron is unstable decays into proton and electron and antineutrino.
(E)(E) True unstable nucleus show radioactivity.

JEE Main question paper PDF

Open a shift to read the full paper on this page, or download it.

JEE Main 2025 Apr 2 Shift 1 question paper

Open Download PDF

Opening paper…

Explain it as a whiteboard videoStep-by-step, in Hinglish or English. Your first video needs no login.Solved it on paper but got it wrong?Upload a photo of your working. Mistake Doctor marks the exact line that broke.
See it move: Atoms: Rutherford, Bohr and X-rays simulationDrag the sliders and watch the numbers in this question change.Revise Modern Physics firstFormula sheet, solved examples and the traps students fall into.

More Physics practice

JEE Main Physics practice question on Atoms & Nuclei (Nuclear structure), with the answer and a step-by-step solution. Scan a question from your own book or paper to get a whiteboard video.