Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Both the Thomson model and the Rutherford model of the atom are unstable.
Reason (R): Thomson’s model is unstable electrostatically, while Rutherford’s model is unstable because its orbiting electrons radiate electromagnetic energy.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Both (A) and (R) are correct and (R) is the correct explanation of (A).
Assertion (A) Both the Thomson model and the Rutherford model of the atom are unstable. — True. Neither model can explain why an atom stays stable.
Reason (R) Thomson’s model is unstable electrostatically, while Rutherford’s model is unstable because its orbiting electrons radiate electromagnetic energy. — True. In Thomson’s model, the electric forces on the electrons cannot give a stable balance. In Rutherford’s model, the electron moves in an orbit, so it is always accelerated. An accelerated charge gives out electromagnetic radiation.
Why Reason (R) explains Assertion (A)?
A says only that both models give an unstable atom. R gives the cause of this instability for each model.
In Rutherford’s model, the radiating electron keeps losing energy, so it should spiral into the nucleus. In Thomson’s model, the instability is electrostatic.
NCERT (2026-27):
Points to Ponder – “1. Both the Thomson’s as well as the Rutherford’s models constitute an unstable system. …”
Points to Ponder – “… Thomson’s model is unstable electrostatically, while Rutherford’s model is unstable because of electromagnetic radiation of orbiting electrons.”