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Elementary Particles

Types of Elementary Particles in Physics

Elementary particles or subatomic constituents, electrons, protons, and neutrons in physics or chemistry are discovered by Scientist Thomson, Golstine, and Chanweak which define the fundamental part of an atom in the periodic table chemical elements. Fundamental particles like proton and neutron located on the positive charge nucleus, electron are the extranuclear subatomic part of an atom carries the negative charge. The smallest discovered elementary subatomic particle is the quark, the basic building block of hadrons. Present-day, the atomic model, properties, and characteristics or types of chemical bonding in learning chemistry or physics is better to describe by the orbital energy level and electron configuration of the elementary subatomic electrons particles of an atom.

The idea about the different types of elementary particles resulted from Faraday’s famous experiment (1837) or electrolysis of salt, acid, and base by the passage of electric current. Faradays establishes the quantitative relations between the amount of electrolysis and the quantity of electricity. He suggested the electric current carry charged elementary particles or ions in the solution. The standard model of different types of elementary subatomic particles was finely developed from the ionization of gases.

Discovery of Elementary Particles (Electrons)

Cathode ray discovery of elementary particles electron proton neutron

Thomson Cathode rays experiment suggested the atoms of periodic table chemical elements contain negatively charged elementary particles. He suggested when gases at low pressures subjected to high potential form various luminous effects. The pressure quite low (0.01 mm), the tube remains dark (Crooks dark space), the rays contain subatomic particles names as cathode rays traveled from cathode to anode with definite properties.

Properties of Cathode Rays or Electron Particles

  1. Production of fluorescence on the opposite wall where the rays impinge.
  2. The rays travel in straight lines confirmed by the shadows of an object placed on their path.
  3. The cathode rays defected from the path they travel by electric or magnetic field. The direction of deflection suggested that the cathode ray carries the negative charge fundamental elementary particle.
  4. When these electromagnetic rays impinge on the crystalline solid metal targets placed on their path x-ray is produced.

Charge and Mass of Electron

The negatively charged elementary subatomic particle electron carries negative charge, e = – 4.8 × 10-10 esu = – 1.60 × 10-19 coulombs. Let the mass of an electron = m and charge = e. Therefore, e/m = 1.76 × 108 coulomb/gram. Mass of an electron particles = (1.60 × 10-19)/(1.76 × 108) gram = 9.11 × 10-28 gram.

Determination of Charge of an Electron

Faraday’s law of electrolysis of silver nitrate is used for the determination of the charge of the subatomic particles electron in physics or chemistry in science. Metallic silver uses as a reducing agent at the cathode by decreasing the oxidation number or gaining one electron.

Therefore, the Avogadro number of electrons produced 1 mole of silver at the electrode from this redox reaction. At the same time, 1 mole of electrons removed from the anode and 1 mole of nitrate ions discharged. But according to Faraday’s law, 96500 coulombs of electrical energy required for the production of 1 gm equivalent of the molecule at the electrode. Therefore, the charge carried by subatomic particles, electron, e = (96500-coulomb mol-1)/(6.023 × 1023 mol-1) = 1.60 × 10-19 coulombs.

Discovery of Protons Particles by Goldstein

Elementary electron contributes negligibly to the mass of the atom but an atom is electrically neutral, hence the nucleus of an atom must contain subatomic particle protons, carries both the mass and positive charge. Goldstein added a new feature to the discharge tubes by using holes in the cathode. With this modification, he observed that there appeared not only cathode rays but also a beam of positively charged particles traveling from anode to cathode. Some of the positively charged subatomic elementary particles passed through the hole in the cathode and produce a spot on the far end of the discharge tube.

Elementary Positive Particles of Atoms

Nature and location of subatomic particles proton found by Thomson in physics or chemistry. On deflection by a magnetic and electric field, the positive ray beam produced a large diffuse spot on the tube. The e/m ratio and velocity of these elementary particles are not the same as electrons. For example, the hydrogen atom is the simplest discovery elementary particles that carry one electron and proton without any neutron.  The nucleus of the hydrogen atom contains an elementary particle proton with a unit positive charge.

Charge and Mass of Proton

The positively charged elementary subatomic particle proton carries positive charge, e = + 4.8 × 10-10 esu = +1.60 × 10-19 coulomb. Let the mass of proton = m and charge = + e. Therefore, e/m = 9.3 × 104 coulomb/gram. Hence the mass of proton = 1.6725 × 10-24 gm

Discovery of Neutron Particles by Chadwick

The entire mass of an atom is concentrated in the nucleus because the weight of electrons being negligible. Atomic number and mass number of hydrogen = 1. Therefore, protons alone account for the total mass of the hydrogen atom.

But except hydrogen, the proton alone cannot account for the total mass of the nucleus. For example, the helium atom 4 times heavy as an atom of hydrogen, hence helium nucleus must be 4 times heavier than the subatomic particles proton. Therefore, to solve these facts Chadwick discovered new fundamental elementary subatomic particles neutron found on the nucleus of an atom. Let the mass number of an atom = A, nuclear charge, or the number of protons of the atom = Z. Therefore, (A – Z) shortfall of the mass number found by other subatomic neutron particles.

Elementary Neutrons and Protons Particles

Rutherford suggested this shortfall must be made up by another elementary particle. Rutherford name this elementary atomic particle in advance as a neutron which is electrically neutral, and mass equal to that of the proton. The glory of the discovery of elementary particles neutron is given the scientist Chadwick, one of Rutherford students. The mass number and the atomic number of oxygen 16 and 8 respectively suggested that the atomic nucleus of oxygen contains the list of subatomic particles like 8 protons or 8 neutrons.

The atoms or species which contains the same number of subatomic proton particles but varying numbers of neutrons inside the nucleus name as isotopes belong to the same atom carries the different types of mass number. For example, protium, deuterium, and tritium are the list of hydrogen isotopes carries zero, one, and two elementary neutron particles with mass numbers, 1, 2, 3 respectively, and isotopes of oxygen (O-16 and O-17) contains eight and nine subatomic neutron particles on the nucleus.