Assertion (A) : If the electrons in an atom were stationary, they would fall into the nucleus.
Reason (R) : An electrostatic force of attraction acts between the negatively charged electrons and the positive nucleus.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Both (A) and (R) are true and (R) is the correct explanation of (A).
Assertion (A) If the electrons in an atom were stationary, they would fall into the nucleus. — True. A stationary electron feels only the attraction of the nucleus, with nothing to balance it, so it would be pulled straight in.
Reason (R) An electrostatic force of attraction acts between the negatively charged electrons and the positive nucleus. — True. Unlike charges attract, so the negative electrons and the positive nucleus attract each other by Coulomb’s law.
Why Reason (R) explains Assertion (A)?
In the Rutherford model the electrons revolve, and the electrostatic attraction supplies the centripetal force that keeps each electron in its orbit.
If an electron were at rest, there would be no circular motion for this attraction to keep up. The unbalanced attraction would then pull the electron towards the nucleus. Hence, the attraction named in (R) is the cause of the fall in (A).
NCERT (2026-27):
Electron Orbits – “The Rutherford nuclear model of the atom which involves classical concepts, pictures the atom as an electrically neutral sphere consisting of a very small, massive and positively charged nucleus at the centre surrounded by the revolving electrons in their respective dynamically stable orbits. The electrostatic force of attraction, Fe between the revolving electrons and the nucleus provides the requisite centripetal force (Fc) to keep them in their orbits.”