Who Discovered the Proton and What Was the Canal Ray Experiment
An atom consists of three subatomic particles which are – Protons, Neutrons and Electrons. Protons and neutrons are found in the nucleus of the atom while electrons are found in the orbits around the nucleus. In this article, we will discuss the discovery of protons in detail but before that you need to know what protons and their fundamental properties are.
What are Protons?
Protons are positively charged fundamental subatomic particles of atoms. Its symbol is p or p+. As we know that a hydrogen atom consists of one proton and one electron, so on removing the electron from the hydrogen atom a proton is produced. That is why protons are also denoted as H+. It possesses +1e (or 1.60 x 10-19 coulomb) positive electric charge. Thus, protons have equal and opposite charge of electrons.
The word Proton is a Greek word which means ‘First’. It was 1st used by Ernest Rutherford in 1920. The subatomic particles protons and neutrons are together known as nucleons. Nucleons form the nucleus of an atom.
What is The Mass of Proton?
The mass of the proton is 1.67 x 10-24 gram or 1.67 x 10-27 kg. As we know the mass of an electron is 9.1 x 10-28 so the mass of a proton is 1836 times the mass of an electron. Although the mass of a proton is almost equal to the mass of a neutron.
Discovery of a Proton
Proton was found at the early stages of the investigations of atomic structure. English chemist William Prout gave Prout’s hypothesis in 1815 in which he proposed that all atoms are composed of hydrogen atoms. He called these hydrogen atoms ‘protyles’. Although it was disproved by various other discoveries and experiments later but set a fundamental base for discovery of various subatomic particles. Then in 1886, German physicist Eugen Goldstein carried out a modified cathode ray tube experiment in which he used electric discharge in a modified discharge tube with perforated cathode. In this experiment he discovered positively charged rays which he named ‘canal rays’. Canal rays are also known as anode rays.
Let us investigate the discovery of protons through a detailed explanation of the Canal Ray Experiment performed by Goldstein.
Canal Ray Experiment: Discovery of Protons
Goldstein used almost the same discharge tube as the cathode ray discharge tube used for discovery of electrons. The point of difference was the perforated cathode used in Goldstein’s canal ray experiment.
Apparatus - Canal ray experiment apparatus consists of a tube (known as anode rays discharge tube) which is made of glass containing two thin pieces of metal, called electrodes, sealed in it. Out of these two electrodes one electrode (or one metal piece) has many holes in it which acts as a cathode while another electrode acts as anode. Both the electrodes are connected to the high voltage generator. The electrical discharge through the gasses could be observed only at very low pressures and at very high voltages. So, the tube was evacuated so that pressure of different gasses could be adjusted. When sufficiently high voltage is applied across the electrodes, current starts flowing through a stream of particles in the tube.
Procedure and Observation – Electric current was passed through both the electrodes which creates an electric field in the tube and ionizes the gaseous atoms in the tube. At this point anode starts emitting positively charged rays which move towards the negatively charged cathode and pass the holes of the cathode and strike the glass walls of the tube at the end near the cathode. These rays produced a faint red glow. These rays were passing in the opposite direction of the cathode rays so it was concluded that the charge they carry must be opposite of cathode rays. As these rays were moving from anode to cathode so called anode rays as well. Due to the same reason the glass tube used in this experiment was called anode ray discharge tube.
The characteristics of positively charged particles of canal rays are listed below –
Unlike cathode rays, mass of positively charged particles depends upon the nature of gas present in the anode ray tube. These are simply positively charged gaseous ions.
The charge to mass ratio of the particles depends on the gas from which these originate.
Some of the positively charged particles carry a multiple of the fundamental unit of electric charge.
The behavior of these particles in the magnetic or electrical field is opposite to that observed for electron or cathode rays in cathode ray’s experiment.
Thus, Eugen Goldstein 1st observed the protons although it was named and identified in other nuclei by British physicist Ernest Rutherford in 1919.
Properties of Protons
Physical properties of protons are as follows –
Charge of a Proton – Protons are positively charged particles. A proton has 1.60 x 10-19 coulomb positive charge which is equal and opposite to that of an electron.
Mass of a Proton – Mass of one proton is equal to that of the mass of one hydrogen atom. As a hydrogen atom contains only one proton in its nucleus and mass of an atom depends on its nucleus. Protons can be produced by removing an electron from a hydrogen atom. The mass of a proton is 1836 times the mass of an electron. Mass of a proton is 1.676 x 10-27 kg or 1.676 x 10-24 g.
Number of protons in an atom possesses its atomic number. For example, hydrogen contains one proton, so its atomic number is 1 while helium contains two protons, so its atomic number is 2.
Protons are spin -½ fermions. This property of protons is used in Proton NMR.
Fun Facts About Proton
Protons live up to 1034 years
Every element or material made in the lab will have at least one proton
Protons help bind nuclei together
Characteristics of Proton
How to Determine the Number of Protons in any Element?
If you want to determine the number of protons, then it is equal to the atomic number of that element. For eg, hydrogen has an atomic number1 hence the number of protons in hydrogen will be 1
Similarly, below is the list of elements with the number of protons in it:
Different Type of Elements and Their Proton Number
Questions that can be asked in the Exam
What is the mass of a proton?
How was the proton discovered?
Give some properties of proton
How many protons do the following elements have?
Hydrogen
Oxygen
Nitrogen
Potassium
Magnesium
Explain in detail the gold foil experiment with a properly labeled diagram.
What color is produced by protons in the cathode ray tube?
What is the composition of the proton?
Explain some main functions of the proton.
This ends our coverage on the topic “Discovery of a Proton”. We hope you enjoyed learning and were able to grasp the concepts. We hope after reading this article you will be able to solve problems based on the topic. If you are looking for solutions to NCERT Textbook problems based on this topic, then log on to Vedantu website or download Vedantu Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests and much more.
FAQs on Discovery Of Proton in Atomic Structure
1. What is the discovery of the proton?
The discovery of the proton refers to the identification of a positively charged subatomic particle present in the nucleus of an atom by Ernest Rutherford in 1917. Rutherford observed that when alpha particles bombarded nitrogen gas, hydrogen nuclei were emitted. He concluded that these hydrogen nuclei were fundamental particles present in other atoms and later named them protons. This discovery helped establish the nuclear model of the atom and explained atomic structure more clearly.
2. Who discovered the proton and in which year?
The proton was discovered by Ernest Rutherford in 1917 during his experiments on nuclear transmutation. In 1917, Rutherford bombarded nitrogen atoms with alpha particles and observed the emission of hydrogen nuclei. By 1920, he formally proposed the name "proton" for this positively charged particle present in atomic nuclei.
3. How was the proton discovered?
The proton was discovered through Rutherford’s alpha particle bombardment experiment on nitrogen gas. The key steps were:
- Rutherford bombarded N2(g) with high-energy alpha particles (He22+ nuclei).
- He observed the emission of hydrogen nuclei.
- The nuclear reaction was: 14N + 4He → 17O + 1H.
- The emitted 1H nucleus was identified as a fundamental positively charged particle, later called the proton.
This experiment proved that hydrogen nuclei are components of other atomic nuclei.
4. What is a proton in chemistry?
A proton is a positively charged subatomic particle located in the nucleus of an atom with a charge of +1. Important properties include:
- Symbol: p+
- Charge: +1.602 × 10-19 C
- Mass: approximately 1.673 × 10-27 kg
- Determines the atomic number of an element
The number of protons defines the identity of an element in the periodic table.
5. What experiment led to the discovery of the proton?
The alpha particle bombardment experiment conducted by Ernest Rutherford led to the discovery of the proton. In this experiment:
- Alpha particles were directed at nitrogen gas.
- Hydrogen nuclei were detected as products.
- The reaction confirmed the presence of a fundamental positive particle inside the nucleus.
This experiment demonstrated artificial nuclear transmutation and revealed the proton as a basic nuclear particle.
6. Why is the discovery of the proton important?
The discovery of the proton is important because it established the concept of the atomic nucleus and explained the identity of elements. Its significance includes:
- Explanation of atomic number as the number of protons.
- Foundation for the modern atomic model.
- Understanding of isotopes (same protons, different neutrons).
- Development of nuclear chemistry and nuclear reactions.
Without the discovery of the proton, the structure and classification of elements would remain unclear.
7. What is the charge and mass of a proton?
A proton has a charge of +1.602 × 10-19 coulombs and a mass of 1.673 × 10-27 kg. Key comparisons include:
- Charge equal in magnitude but opposite to an electron.
- Mass approximately 1836 times greater than an electron.
- Nearly equal in mass to a neutron.
These properties make the proton a major contributor to atomic mass.
8. How does the number of protons determine an element?
The number of protons in the nucleus determines the atomic number and identity of an element. For example:
- Hydrogen has 1 proton → Atomic number 1.
- Carbon has 6 protons → Atomic number 6.
- Oxygen has 8 protons → Atomic number 8.
Changing the number of protons changes the element itself, which is why atomic number is the fundamental basis of the periodic table.
9. What is the difference between a proton, neutron, and electron?
The main difference between a proton, neutron, and electron lies in their charge, mass, and location in the atom. Key differences are:
- Proton (p+): +1 charge, located in nucleus, mass ≈ 1 amu.
- Neutron (n0): 0 charge, located in nucleus, mass ≈ 1 amu.
- Electron (e-): −1 charge, located in electron cloud, very small mass.
Protons and neutrons form the nucleus, while electrons occupy energy levels around it.
10. Did Rutherford discover the proton before the neutron?
Yes, Rutherford discovered the proton before the neutron; the proton was identified in 1917, while the neutron was discovered later by James Chadwick in 1932. Rutherford’s work revealed the positively charged particle in the nucleus, but the existence of a neutral particle (neutron) was confirmed 15 years later to explain atomic mass and isotopes.
