Question

The ratio of the mass of the proton to the electron is about:
(a) $1.8\text{ x 1}{{\text{0}}^{-3}}$
(b) $1.8\text{ x 1}{{\text{0}}^{3}}$
(c) 1
(d) 0

Answer 1

Hint: An electron is a fundamental particle that has a negative charge and the mass of the electron is $9.11\text{ x 1}{{\text{0}}^{-28}}\text{ g}$, and a proton is a fundamental particle that has a positive charge and the mass of a proton is $1.67\text{ x 1}{{\text{0}}^{-24}}\text{ g}$.

Complete step by step answer:
Let’s study proton and electron:
We know that an atom is electrically neutral, so it must be having an equal amount of negative and equal amount of positive charge. So the positive charge in an atom is due to the presence of protons.
So, we can say that a proton is a fundamental particle that has a unit positive charge.
Protons were discovered from anode rays. When high voltage is passed between the electrodes then it was found that some rays were coming from the side of the anode which passed through the holes in the cathode and produced green fluorescence. These rays were called anode rays or canal rays or positive rays (because of the presence of positive atoms).
The charge of a proton is $1.6\text{ x 1}{{\text{0}}^{-19}}$C and the mass of a proton is $1.67\text{ x 1}{{\text{0}}^{-24}}\text{ g}$.
The negative part of the atom is due to the presence of electrons so we can say that an electron is a fundamental particle that has one unit negative charge.
Electrons were discovered from cathode rays. When high voltage is passed between the electrodes it was found that at very low-pressure rays from the cathode were passed to the hole of the anode which had faint greenish color. These were called cathode rays and carry a negative charge (because of the presence of electrons).
The charge of the electron is $-1.6\text{ x 1}{{\text{0}}^{-19}}$C and the mass of the electron is $9.11\text{ x 1}{{\text{0}}^{-28}}$g.

So, the ratio of the mass of the proton to the mass of an electron is:
$\dfrac{1.67\text{ x 1}{{\text{0}}^{-24}}}{9.11\text{ x 1}{{\text{0}}^{-27}}}=1835$
Or it can be written as: $1.8\text{ x 1}{{\text{0}}^{3}}$
So, the correct answer is “Option B”.

Note: Both the rays i.e., anode rays and cathode rays travel in a straight line. The mass of both particles was calculated by dividing the charge to the ratio of charge/mass:
$m=\dfrac{e}{e/m}$ .
The ratio of charge/mass of a proton is $9.58\text{ x 1}{{\text{0}}^{4}}C/g$ and that of the electron is $1.76\text{ x 1}{{\text{0}}^{8}}C/g$.