Question

These questions concern the work of J. J. Thomson:
a.From Thomson's work, which particles do you think he would feel are most important for the formation of compounds (chemical changes), and why?
b. Of the remaining two subatomic particles, which do you place second in importance performing compounds and why?
c. Propose three models that explain Thomson's findings and evaluate them. Include Thomson's findings.

Short answer

Answer

The three subatomic particles are electrons, protons, and neutrons.

1. Electrons are the subatomic particles that participate in the formation of compounds.
2. The next subatomic particles that are important are protons which are positively charged.
3. Millikan oil-drop method, Rutherford’s alpha scattering experiment, and radioactivity explain Thomson’s postulates.

Step-by-step solution

Thomson’s postulates

According to Thomson’s atomic model, the electrons are enclosed in the positive charge, similar to the seeds in the watermelon. Seeds represent the electrons, and the flesh of the melon represents the positive charge.

Existence of electrons in an atom by Thomson’s model

The postulates of Thomson will lead to the electron existence in an atom. Thomson assumed that the atom had a positive charge due to which the atom was neutral. This is due to the existence of positively charged protons and is considered a second priority.

Millikan oil drop method

The determination of the charge to mass ratio by Thomson can be defined from the deflection measurement of an electron beam in a magnetic field.

$\frac{e}{m}$= - 1.76 $\times$ 10⁸ C/g

It helps in the calculation of the electron charge. This $\frac{e}{m}$ value was used for the determination of electron mass from Thomson’s experiment.

Support of Thomson proposal and radioactivity

Thomson proposed that the atom consists of both positively and negatively charged electrons with the emission of $\alpha$ and $\beta$ particles, which supported his proposals.

α -ray scattering experiment

Thomson performed an experiment for the testing of the plum pudding model. If this theory were perfect, the atom would have allowed all the $\alpha$- particles to pass. There is an accumulation of positive charge due to the repelling of $\alpha$- particles. This gave rise to the new invention of the planetary orbital model.