Electron Proton Neutron:- During the past hundred years, scientists have made contributions, which helps in the development of the modern theory of atomic structure. The work of J.J. Thomson and Ernst Rutherford actually laid the foundation of the modern picture of the atoms. It is now discovered that the atoms contain several particles called some atomic particles like electrons, protons, neutrons, positrons, neutrino, meson, etc. Out of these particles, the electron, proton, and neutron called fundamental particles and are the binding blocks of the atoms.
Discovery of Electron Proton Neutron:-
The nature and existence of electrons established by experiment on the conduction of electricity through gases. In 1859, Julius Plucker started the study of the conduction of electricity through gases at low pressure in a discharge tube. The air almost completely removed from the discharge tube (pressure about 10-4 atmosphere). When a high voltage of the order of 10000 volts or more passed across the electrodes. Some sorts of individual rays moved from the negative cathode to the positive electrode. Since, The negative electrode referred to as cathode these they called cathode-ray further investigation word made by W. Crooks, J. Perrin. J.J. Thomson and others. Cathode rays cause the following properties-
Properties of electrons/Cathode rays
- They travel in a straight line away from the cathode with very high velocity is ranging from 10 9 to 10 11 per second.
- This ray shows the shadow of metallic objects placed in the path of the cast on the wall opposite to the cathode ray.
- They produce a green glow when it strikes the glass wall beyond the anode light is emitted when there is strike the zinc sulfide screen.
- They produce heat energy when they collide with the matter it shows that cathode ray causes kinetic energy converted into heat energy when stopped by matter.
- Cathode rays produce X rays when this falls on a material having higher atomic mass.
- These rays affect the photographic plate.
- Cathode ray can penetrate through in foils of solid material and causes ionization in gases through which they pass.
Important notes of electrons/Cathode rays
- Cathode rays carry a negative charge thus the name electron given by Stoney.
- In 1897, J.J. Thomson determined the e/m value (charge/mass) of the electron by studying the deflection of cathode-ray in an electronic and magnetic field the value of e/m has been found to be- 1.7588 x 108 coulomb/g.
- The first precise measurement of the charge on the electron was made by Robert A. Millikan in 1909 by oil drop experiment the charge of an electron was found to be -1.6022 x 10-19 coulomb. Since an electron, the smallest charge knew it was thus designed as a unit negative charge.
Calculation of Electrons-
Mass of the Electron:- The mass of the Electron can be calculated from the value of e/m and the value of electron.
This is termed as the rest mass of the electron i.e. mass of the electron when with low speed. Mass of the Moving Electron:-
where v is the velocity of the electrons and c is the velocity of light. When v becomes equal to c, The mass of the moving electrons becomes infinity. What is Electromagnet and Its Uses and Properties?
Discovery of Proton
With the discovery of electrons, Scientists started looking for positively charged particles which where naturally respected becomes matter is electrically neutral under ordinary coordination. the first experiment that led to the discovery of the positive particle was conducted by Goldstein in 1886. He uses a perforated cathode in the modified cathode ray tube. it was observed that when a high potential difference was applied between the electrodes, not only cathode rays produced but also are new types of rays were produce simultaneously from a node moving towards the cathode and passed through the whole of the canal of the cathode. These rays were termed canal Ray, sense, these pass through the canal of neck cathode. This named indoors as this originates from the anode. The following characteristic of the positive rays.
- The rays travel in a straight line and cast a shadow of the object placed in their path.
- Like cathode rays, these rays also rotate the wheel placed in their path and also have a heating effect.
- The rays produce flashes of light on zinc sulphide screen.
- These rays can pass through thin metal foils.
- These capable of producing physical and chemical change.
- This ray can produce ionization in gases.
Calculation of Proton
JJ Thomson made accurate measurements of the charge and the mass of the particles obtained in the discharge tube containing hydrogen, the lightest of the gases, in 1906. These particles found to have the e/m value as +9.579 x 104 coulomb/g. Rutherford renamed the positive particles in 1911. The protons carries a charge +1.602 x 10-19 coulomb, i.e. one unit positive charge. The mass of the proton thus can calculate.
The mass of the proton in AMU (Atomic Mass Unit)
discovery of neutron
The discovery of neutron was actually made about twenty years after the structure of atoms was elucidated by Rutherford. Atomic masses of different atoms could not be explained if it was accepted that atoms consisted only of protons and electrons. Thus, rutherford suggested in 1920, that in atoms, there must be present at least of the third type of fundamental particles which should be electrically neutral and forces mass nearly equal to that of the proton. They proposed the name of such fundamental particles like the neutron. In 1932, Chadwick bombarded beryllium with a stream of Alpha particles. He observed that penetrating radiations were produced which were not affected by electric and magnetic fields. This radiation considered as neutral particles which were called neutrons the nuclear radiation can be a source as-
The mass of neutrons was determined it was 1.675 x 10-24 g. A neutron is a subatomic particle that has a mass of 1.675 x 10-24 g. The e/m value of neutrons is zero.
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