Question

Which pairing below does not correctly match the scientist with the contribution to the understanding of the atom? A. Proust and the realization that the elements of compounds are found in certain proportions by mass B. Rutherford and the understanding that the atom has a small, dense nucleus with a positive charge C. Thomson and the law of definite proportions D. Dalton and the initial proposal of the atomic theory of matter

Answer 1

The answer would be C. In fact, letter A already defines the Law of Definite Proportions. On the other hand, J.J. Thomson was responsible for the discovery of electrons through cathode ray tube experiments. The rest of the choices are true.

Answer 2

Answer is: C. Thomson and the law of definite proportions.

1) J. J. Thomson discovered the electron in 1897.  

His "plum pudding" model (1904) suggested: the electrons are embedded in the positive charge.  

2) Rutherford demonstrate that J.J Thompson's Plum Pudding model was not accurate.

Rutherford theorized that atoms have their charge concentrated in a very small nucleus.

3) Proust's law or law of constant composition said that a given chemical compound always contains its component elements in fixed ratio and does not depend on method of preparation.

4) Dalton's atomic theory:

a) All matter consists of indivisible particles called atoms.  

b) Atoms of the same element are similar in shape and mass, but differ from the atoms of other elements.  

c) Atoms cannot be created or destroyed.  

d) The ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers.  

e) Atoms of same element can combine in more than one ratio to form two or more compounds.  

f) The atom is the smallest unit of matter that can take part in a chemical reaction.