Question Video: Recalling What Landmark Scientific Experiments Proved and What They Disproved | Nagwa Question Video: Recalling What Landmark Scientific Experiments Proved and What They Disproved | Nagwa

Question Video: Recalling What Landmark Scientific Experiments Proved and What They Disproved Chemistry • Second Year of Secondary School

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Which of the experiments listed below did not match its given conclusion?

03:12

Video Transcript

Which of the experiments listed below did not match its given conclusion? (A) The Rutherford experiment was useful in determining the nuclear charge on the atom. (B) The Rutherford experiment confirmed the presence of a positively charged nucleus in the center of the atom. (C) The Rutherford experiment proved the Thomson plum pudding model of the atom to be essentially correct. (D) Thomson’s work on the electric discharge tube showed the existence of negatively charged particles called electrons. Or (E) Millikan’s oil drop experiment determined the charge of the electron.

The three main scientists behind the experiments listed are Rutherford, Thomson, and Millikan. All three contributed crucial conclusions toward atomic theory. Let’s have a look at their major experiments to identify the correct answer.

Thomson’s work with cathode rays or electric discharge tubes allowed him to suggest his plum pudding model. Through his work, he concluded that atoms contain negatively charged subatomic particles called electrons. His model suggested that these electrons were contained within atoms in an evenly distributed positive charge. Since the question is asking us to identify the answer choice that does not match the experiment to its conclusion, we can eliminate answer choice (D), which does describe Thomson’s conclusion.

Armed with the information that negatively charged subatomic particles exist, Millikan’s work with charged oil droplets revealed the behavior of these charged particles. This experiment led to the determination of an electron’s charge, so we can eliminate answer choice (E).

Rutherford’s gold foil experiment was groundbreaking, and it yielded unexpected results, which eventually led to the discovery of the positively charged nucleus. By firing positively charged 𝛼 particles at a thin sheet of gold, Rutherford was able to put Thomson’s plum pudding model to the test. If the positive charge were evenly spread in the atom, the 𝛼 particles fired at the gold atoms would pass through. However, on a detecting screen, it was found that many passed through, some were slightly deflected, and some were significantly deflected. This led to the conclusion that atoms contain a dense center or a nucleus that is positively charged. So we can eliminate both answer choices (A) and (B).

Since Rutherford’s gold foil experiment essentially proved Thomson’s model to be incorrect, the answer choice that lists an experiment that does not match its conclusion is answer choice (C). The Rutherford experiment proved the Thomson plum pudding model of the atom to be essentially correct.

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