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# Thermonuclear Fusion

There are three possible states of matter that is solids, liquids and gases. Each state is composed of atoms and if there is only one type of atom in any material than it is called a chemical element or a basic element or an element.

Hence an atom is the smallest particle or building block of any element that still retains its identity in that element. One atom always is same in any element as it always has the same number of protons, electrons and neutrons. The difference in chemical and physical properties of different atoms is due to the different numbers of protons.

Thermonuclear process is the process in which a star produces its light, heat, and huge amount of energy.

## Sub Atomic Particles

The smallest particle of matter which can be exist in nature is known as atom. Professor Henri Becquerel proved that each atom is un dividable particle. Each atom consist of three basic particles; electron, proton and neutron. These particles are known as subatomic particles.

## Define Sub Atomic Particles

The particles present in an atom are called as subatomic particles. Subatomic
particles can be two types.
1. Elementary particles
2. Composite particles.

### Elementary subatomic particles

Some example of elementary particles are
• Six quarks: Up, down, bottom, top, strange, and charm.
• Six types of leptons:  tau neutrino,  electron neutrino, electron, muon,  tau, muon neutrino,
• Thirteen gauge bosons: the photon, the three W and Z bosons, the graviton of gravity and the eight gluons.

### Composite Subatomic Particles

They are bound states of two or more elementary particles. For example, a proton is produced due to the combination of two up quarks and one down quark. In the same way helium-4 is made up of two protons and two neutrons. Composite particles include all hadrons, a group composed of baryons (e.g., protons and neutrons) and mesons (e.g., pions and kaons).

On the basis of stability, subatomic particles can be two types.

### Stable Particles

These particles are stable and cannot further decompose in atom. They can be mass less or with certain mass. There are total seven stable particles in an atom;

 Particle Symbol Charge Spin 1 Electron e- , $\beta^{-}$ -ve $\frac{1}{2}$ 2 Proton p +ve $\frac{1}{2}$ 3 Positron e+ , $\beta^{+}$ +ve $\frac{1}{2}$ 4 Neutrino U 0 $\frac{1}{2}$ 5 Antiproton p- -ve $\frac{1}{2}$ 6 Graviton G 0 2 7 Photon 0 1

Let’s discuss some stable subatomic particles.

### 1. Proton

• Goldstein in 1886 canal rays or anode rays and proved that they were positively charged particle which produced from gases discharged at high pressure.
• J.J.Thomson called these rays as positive rays since they are made up of positively charged particles.
• The e/m ration of for these positively charged particles depend upon the nature the gas filled in discharge tube. Further experiments proves that the mass of lightest positive charge particle is equals to the mass of one hydrogen atom or 1837 times more than the mass of electron.
• This particle termed as proton. Proton represented by H+ or p. They are positively charged particles placed at part of the dense nucleus along with neutrons.
• The mass of each proton is 1.0073 amu. The number of protons per atom determines the atoms element or atomic number.
• Since electrons have negligible mass, hence  proton make up most of the mass if the atom along with neutrons  and make up a small part of the atoms overall volume. Some other properties of proton are;

 Properties Proton Charge by mass ration 9.758 x 104 c/gm Mass 1.6725 x 10-24 gm Charge 1.6 x 10-19c Mass in amu 1.00757 amu Gram molar mass 1.008

### 2. Electron

• Willium crooks and J.J.Thomson discovered cathode rays which are made up of negatively charged particles called as electrons. They are negatively charged particles which move freely in the atom.
• The mass of electrons is around 5.486 x 10-4. The charge by mass ration of electrons is called as specific charge and it is equals to 9.1091 x 10-28 gm.
• The charge on one mole of electron is equals to one faraday that is equal to 96500 coulombs.
• Since electrons are basic particles of any atom hence loss, gain, and sharing of electrons important in many chemical reactions.
• The electrons present in the valence shell decide the physical and chemical properties of any atom.
• Electrons revolve in certain orbits around the nucleus which is determined by the electrons quantum numbers.
Some other properties of electron are as follows.

 Properties Elelctrons Charge by mass ration 1.76 x 108 c/gm Mass 9.1091 x 10-28 gm Charge 1.6 x 10-19c Mass in amu 0.0005486  amu Gram molar mass 5.483 x 10-4 Number of electrons in one gram 1.1 x 1027

### 3. Unstable Subatomic Particles

• These subatomic particles are not stable and show decay in certain nuclear reaction.
• For example, Neutron was first discovered by Jams Chadwick during the study of penetrating rays.
• They have no charge (neutral) and become a part of the dense nucleus along with protons.
• The mass neutron is 1.0087 amu which is almost equals to the mass of hydrogen atom.
• The atomic mass of any atom is equals to the sum of mass of protons and neutrons.
• Along with protons in the nucleus, neutrons make up a small part of the atoms overall volume.
Some other unstable subatomic particles are as follows;

 Particle Symbol Charge 1 Neutron n 0 2 Negative μ meson μ- -ve 3 Positive μ meson μ+ +ve 4 Negative π meson π- -ve 5 Positive π meson π+ +ve 6 Neutral π meson π 0 7 Positive χ meson χ+ +ve 8 Negative  χ meson χ- -ve 9 ξ  meson ξ ± 10 τ meson τ ± 11 Κ meson Κ ± 12 Negative V meson V- -ve 13 Positive V meson V+ +ve 14 Neutral V meson V 0

## Sub Atomic Particles List

 Particle Symbol 1 Electron e- , β- Stable subatomic particles 2 Proton p 3 Positron e+ , β+ 4 Neutrino υ 5 Antiproton p- 6 Graviton G 7 Photon 8 Neutron n Unstable subatomic particles 9 Negative μ meson μ- 10 Positive μ meson μ+ 11 Negative π meson π- 12 Positive π meson π+ 13 Neutral π meson π 14 Positive χ meson χ+ 15 Negative χ meson χ- 16 ξ meson ξ 17 τ meson τ 18 Κ meson Κ 19 Negative V meson V- 20 Positive V meson V+ 21 Neutral V meson V

## Mass of Sub Atomic Particles

 Particle Symbol Mass (a.m.u) Mass with respect to electron mass = 9.11 x 10-28gm 1 Electron e- , β- 0.0005486 1 2 Proton p 1.00758 1.836 3 Positron e+ , β+ 0.0005486 1 4 Neutrino U <0.000022 < 0.04 5 Antiproton p- 1.00758 1.836 6 Graviton G 0 0 7 Photon 0 0 8 Neutron n 1.00893 1.8385 9 Negative μ meson μ- 0.1152 210 10 Positive μ meson μ+ 0.1152 265 11 Negative π meson π- 0.1514 276 12 Positive π meson π+ 0.1514 276 13 Neutral π meson π 0.1454 265 14 Positive χ meson χ+ 0.7680 1400 15 Negative χ meson χ- 0.7680 1400 16 ξ meson ξ 0.3018 550 17 τ meson τ 0.5349 975 18 Κ meson Κ 0.6035 1100 19 Negative V meson V- 1.2069 2200 20 Positive V meson V+ 1.2069 2200 21 Neutral V meson V 0.41643 850

## Nuclear Reactions

Just like chemical reactions, nuclear reactions are also express by equations although in a unique different manner compare to chemical reactions. A chemical reaction involves different electrons of an atom while atomic nucleus takes part in nuclear reactions. For representing an element involves in reaction is identified by the chemical symbol.

There are two numbers in any chemical symbol,
1. Mass number that is the sum of number of protons and neutrons written as A at the upper right of chemical symbol.
2. On the other hand, the number at the lower left is the atomic number (Z) describes as the number of protons in the nucleus and determines the type of atom. For example the symbol for Uranium-238 will be 92U238

Where atomic number is 92 and mass number of uranium is 238. There is no change in the nuclear structure of atomic species taking part in the chemical reactions while nuclear reactions involve changes in the number of nucleons and formed new atomic species. Hence nuclear reactions lead to the atomic transformation or transmutation.

Nuclear reactions involve energies a million times greater than involved in chemical reactions. This is because of measurable loos of mass in nuclear reactions, estimated as mass defect. Generally some particles like alpha and beta particles involve in nuclear reactions. The symbol for an alpha particle is 2He4 and for a beta particle is -1e0. While the chemical symbol for a neutron is 0n1.

Let’s take an example of nuclear reaction of conversion of Uranium-238 to Thorium and gamma rays through the alpha decay. This is expressed mathematically by the following equation.

92U23890Th234 + 2He4 + gamma rays

Like any other chemical reaction, in nuclear reaction also the mass numbers on each side of the equation are added together that they are equal and same concept is applicable for the atomic numbers also. Other example of nuclear reaction is bombarding of nitrogen nucleus with an alpha particle to produce oxygen atom and hydrogen atom.

2
He4 + 4N14 8O17 +1H1

Nuclear reactions can be classified in four types.
1. Nuclear fusion
2. Nuclear fission
4. Artificial Transmutation
1. Nuclear Fusion is a fusion reaction of lighter elements to form heavier ones. For example; the fusion of two hydrogen atoms form helium atom with one positron and some amount of energy as generally nuclear fusion reactions are highly exothermic in nature, hence they are the main source of energy for the sun, and are also used in certain types of nuclear weapons.

1
H 1 + 1H1 1H2 + 1e0

Other example of nuclear fusion reaction is fusion of deuterium with tritium to form helium and neutron. This fusion releases 17.6 MeV of energy and used in hydrogen bomb.

2. Nuclear Fission is a fission reaction of heavier elements into lighter elements due to the bombardment of energetic particles like neutrons. In this nuclear reaction the parent nucleus splits into several smaller fragments which are about equal to half the original mass and two or three neutrons are also emitted.

For example, fission of uranium because of bombardment of neutron produces barium, krypton and three neutrons with large amount of energy.

0n1 + 92U235 56Ba141 + 36Kr92 + 3 0n1

Such type of nuclear reactions is chain reaction and proceeds spontaneously due to the production of 3 neutrons which can be further react with uranium nucleus. Other nuclei used for nuclear fission are uranium-233 and plutonium-239. Nuclear fission reactions are widely used in production of energy in atomic bomb and nuclear power station.

3. Radioactive Decay occurs in radioactive elements which can decay spontaneously. The rate of decay of radioactive elements is not depending on the temperature and pressure or on any external conditions. A certain constant fraction of radioactive sample undergoes change in unit time. The decay or disintegration of radioactive element can be measured by using their half life time which is the time during which half of the amount if given sample disintegrated. For example; half life time period for Radium (Ra) is 1590 years.

Some examples of radioactive decay are;

92U238 90Th234 + 2He4
90 Th234
91Pa234 +-1e0

Radioactive decay always involves emission of some light weight particles like alpha, beta, neutron particles or gamma rays.

4. Artificial Transmutation reaction brought about artificially through the interaction of two nuclei. This type of reactions is initiated by bombarding a relatively heavier nucleus with lighter nuclei. Generally lighter nucleus is protium, deuterium or helium particles. While the heavy nuclei produced in reaction may or may not be stable and can be further decay in another nuclei.

These reactions are also called as artificial radioactivity. Some examples of artificial transmutation are as follows.

7N14 + 2He4 8O17 + 1p1
27Co59 + 0n1
27Co60
11Na23 + 0n1
11Na24
92U238 + 0n1
92U239 93Np239 + -1e0