Question

mastering chemistry Based on the data Thomson collected in his experiments using cathode rays, the concept of atomic structure was modified. Which of the following statements about the atomic structure were validated by his cathode ray experiments?

Answer 1

The list of choices from which you have to check all that apply is:

• Particles of the cathode rays are fundamental to all matter.

• In the atom, the particles of the cathode rays are embedded in a diffuse cloud of positive charge.

• Matter contains negative charge and by inference positive charge.

• There are subatomic size particles in an atom.

• Cathode rays have mass.

Answer:

The correct choices are:

• Particles of the cathode rays are fundamental to all matter.

• Matter contains negative charge and by inference positive charge.

• There are subatomic size particles in an atom.

• Cathode rays have mass.

Explanation:

From the five statements, only the second one, In the atom, the particles of the cathode rays are embedded in a diffuse cloud of positive charge, is not validated by the data Thomson collected in his experiments.

Nevertheless, he conjectured that that was the right structure and proposed the famous Plum Pudding Model of the atom, which ended not being correct.

The cathode rays are streams of negatively charged particles produced in an electrode. As, those rays did not change for different kind of electrodes or gases, it was concluded that they were present in all the forms of matter. So, this validate the first statement, Particles of the cathode rays are fundamental to all matter.

Thomson determined the ratio charge/mass for these particles of the cathode rays and found that the mass was much smaller than the mass of the lightest atom (hydrogen atom). This meant that there were particles smaller than the atom. This validates the fourth and fifth statements: There are subatomic size particles in an atom and Cathode rays have mass.

Since, the matter is electrically neutral, the fact that there are negative particles meant that there are also positive charges that balance the charge of the atom making in neutral. This is the third statement Matter contains negative charge and by inference positive charge.

As already stated, this does not say where and how the negative and positive charges are in the atoms, so the second statement, In the atom, the particles of the cathode rays are embedded in a diffuse cloud of positive charge, is not validated by the data Thomson collected.