Proton Mass

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Proton is an elementary subatomic particle which is identical with the nucleus of the hydrogen atom and is made up of current quarks. It is denoted by p or p+. The location of Proton is inside the nucleus only and the charge of proton is positive that is +1e elementary charge. The Proton mass is slightly less than the neutron mass and mass of proton can be measured using the units kg,MeV/c, and u (amu). Proton along with the neutron is a constituent of all other atomic nuclei, that carries a positive charge.Both Protons and neutrons, each with masses of one atomic unit approximately they are together referred to as nucleons (particles present in atomic nuclei).


Mass of Proton 

The mass of the proton is the sum of the total mass of current quarks and the binding gluons. Protons and neutrons are made up of smaller particles and are classified as baryons—particles composed of three elementary units of matter known as quarks and the strong interaction between these sub-particles is mediated by the exchange of massless particles called gluons that act between quarks.


The Mass of the Proton is

Proton Mass mp = 1.672621898(21)×10−27 Kg


Mass of Proton in Other Units

The mass of the proton can be denoted in a number of units like – proton mass amu, mass of proton in kg, proton mass MeV. 

The proton mass in different units are as follows:

Mass of proton in kg is 1.672621898(21)×10−27 kg

Mass of proton in grams is 1.672621898(21)×10−24 g

Mass of proton in amu is 1.007276466879(91) u

Mass of proton or proton mass in MeV is 938.2720813(58) MeV/c2


Proton Mass Calculation 

Goldstein in the year 1886 in his experiment noticed that the charge to mass ratio of the positive particles depends on the nature of the gas which is present in the discharge tube which means that the charge to mass ratio (e/m) is different for the different gases. He observed that the charge to mass ratio of the positive rays was more in case of the hydrogen gas, was used in the discharge tube which was mainly because hydrogen is the lightest atom so m will be the least thus the e/m ratio will be more or highest in this case. These particles in the positive rays in the discharge tube were later named as a proton.  We can also say that a proton can be produced by removing an electron from the hydrogen atom. Thus, it can also be said that proton is a hydrogen ion (H+).

There Are Three Methods That Use Different Approaches to Find the Atomic Mass of a Proton. These Three Methods Are:

  1. Calculation from theory

  2. Atomic Mass Method

  3. Charge/Mass comparisons with electron

1. Calculation from Theory: Albert Einstein came up with his revolutionary theory, “the theory of relativity” during the 20th century. The theory brilliantly explained that mass and energy are interchangeable; the mass can be converted into energy and vise-versa. In this method, we derive the mass of protons from the above-mentioned theory. 

Protons have an internal structure- three forces (quarks) that hold together with attraction forces (gluons). Now according to the naive norms, they would give each quark about 1/3 mass of a proton. But, in reality, quark mass does not contribute 95 to 98% of the mass of a proton.

In reality, most of the mass of a proton is derived from interaction energy between the quarks using the mass and energy are interchangeable theory i.e. E =mc2.


2. By Atomic Molar Mass Method: In the hydrogen atom one mole or 6.02214076×1023 particles weighs 1.0079 g thus each mole of proton in one hydrogen atom weighs 1.0079g. 

Since one mole equals 6.02214076×1023 particles, and we know that protons weigh 1.0079 g. Then dividing the weight of the proton with the mole number we get (1.0079 /6.022×1023) Thus the proton mass equals 1.6737×10-24 g.

Note: in the atom, there is an electron to balance the proton charge. Also, we can do this experiment with any element of the periodic table.


3. Charge/Mass Comparisons with Electron: In this method, the atom’s bend is measured when it enters the standardized electric and magnetic fields. In addition, the bending magnitude also indicates the proton mass by comparing it with electron mass. The main idea of an experiment is similar to inducing the motion of a rolling ball where a constant force (mechanical force) will always deflect a heavy proton from a straight-line movement to a small extent. This deflection in electrons is even more. 

FAQ (Frequently Asked Questions)

1. Who Discovered Protons and When?

Goldstein found that the charge to mass ratio of the positive particles depends on the nature of the gas which is present in the discharge tube in the year 1886 and the particles in the positive rays in the discharge tube were named as a proton. Also, a proton can be produced when we remove an electron from the hydrogen atom.

2. What is Inside the Proton?

The proton is one of the fundamental particles of an atom and it consists of basic sub-particles called quarks and gluons. Protons have an internal structure- three forces (quarks) that hold together with attraction forces (gluons).

3. How is the Mass of Proton Related to the Hydrogen Atom?

The mass of a proton is equal to the hydrogen atom as the hydrogen atom consists of one proton and one electron. As the mass of an electron is considered to be negligible, therefore, it can be said that the mass of a hydrogen atom is the same as the mass of a proton and with respect to an electron the mass of a proton is 1840 times the mass of an electron.

4. Which Experiment Found the Proton?

Rutherford found protons in 1909 in his famous gold foil experiment.