Choose the correct options and explain the reason for the correct and incorrect options. Class 9
Choose the correct options and explain the reason for the correct and incorrect options. Class 9
Revise, Reflect, Refine (Page 158-160)
Question 1.
Choose the correct options and explain the reason for the correct and incorrect options in the context of Ernest Rutherford’s gold foil experiment: Class 9
(i) The experiment clearly showed the existence of neutrons in the nucleus.
(ii) The results disproved the plum pudding model and led to the idea of a nucleus at the centre of the atom.
(iii) The large deflection of a few alpha particles indicated that most of the mass of the atom and positive charge are packed into a tiny centre.
(iv) The way alpha particles were deflected showed that electrons are around the nucleus.
Answer:
(i) Incorrect. The gold foil experiment did not show the existence of neutrons. Neutrons were discovered by James Chadwick in 1932, much later, through a completely different experiment. The gold foil experiment only revealed the existence and nature of the nucleus (positively charged and dense).
(ii) Correct. The gold foil experiment's results - that most alpha particles passed through undeflected but some were sharply deflected and a few bounced back - could not be explained by Thomson's plum pudding model (where positive charge is spread out). These results disproved the plum pudding model and led Rutherford to propose the idea of a small, dense, positively charged nucleus at the centre of the atom.
(iii) Correct. A few alpha particles bounced back sharply, which is only possible if they encountered a very small but extremely dense and strongly positive', region. If the positive charge were spread out (as in Thomson's model), no alpha particle would bounce back. The large deflection of a few alpha particles confirmed that most of the mass-and all the positive charge are packed into a tiny centre called the nucleus.
(iv) Incorrect. The gold foil experiment did not show or study the movement of electrons around the nucleus. It only revealed information about the nucleus - its size, charge, and density. The movement of electrons in orbits around the nucleus was proposed by Rutherford's model as a logical conclusion, but the experiment itself did not directly demonstrate this.