Nuclear Chemistry and Application of Radioactivity : Notes_ Unit 21 _ Class 12 Chemistry Notes PDF

Unit 21

Nuclear Chemistry

Nuclear Chemistry:

·         The branch of chemistry which deals with the study if nuclear fusion, fission, radioactivity is known as nuclear chemistry.

Radioactivity

·         The phenomenon of emission of radiation like alpha (α), beta(β) and gamma(γ) by disintegrating mass of heavy unstable nuclei spontaneously is known as radioactivity.

Example:

                                Emission of radiation by uranium.

Types of Radioactivity:

                On the basis of occurrence of phenomenon, radioactivity is of two types:

i.                     Natural Radioactivity

ii.                   Artificial Radioactivity

i.                    Natural Radioactivity:

The phenomenon in which naturally existing heavy nuclei like uranium, thorium, actinium, radium etc. spontaneously emits radiation (α, β, γ-rays) till it become stable is known as natural radioactivity.

Example:

                ₉₂U²³⁹ à ₉₀Th²³⁴ + ₂He⁴ (α-rays) 

ii.                   Artificial Radioactivity:

The phenomenon of emission of radiation like alpha (α), beta(β) and gamma(γ) rays from artificial radioactive nuclei by disintegrating mass till it become stable is known as artificial radioactivity.

Example:

₁₃Al²⁷ + ₂He⁴ à₁₁Na²³ + ₂He⁴

Difference Between Natural and artificial Radioactivity

S. No	Natural Radioactivity	Artificial Radioactivity
1.	The phenomenon in which naturally existing heavy nuclei like uranium, thorium, actinium, radium etc. spontaneously emits radiation (α, β, γ-rays) till it become stable is known as natural radioactivity.	The phenomenon of emission of radiation like alpha (α), beta(β) and gamma(γ) rays from artificial radioactive nuclei by disintegrating mass till it become stable is known as artificial radioactivity.
2.	It cannot be controlled.	It can be controlled.
3.	It occurs in heavy unstable nuclei like uranium, thorium etc.	It occurs in lighter radioactive isotopes.
4.	It is comparatively slower.	It is comparatively faster.
5.	It generally emits heavy rays like α, neutrons.	It generally emits lighter rays such as β-rays, γ-rays etc.
6.	Example: 92U239 à90Th234+ 2He4 (α-rays)	Examples: 13Al27 + 2He4 à11Na23 + 2He4

 

Unit Of Radioactivity:

·         Activity of radioactive substance is determined in terms of disintegration per seconds (dps). Basically, there are three types of units of radioactivity and they are:

i.                    Becquerel (Bq):

It is the activity of amount of radioactive substance that undergoes one disintegration per second.

It is denoted by Bq.

ii.                   Curie (Ci):

It is the activity of amount of radioactive substance that undergoes 3.7*10¹⁰ disintegration per second.

It is denoted by Ci.

1 Ci         = 3.7*10¹⁰ dps = 3.7*10¹⁰Bq

iii.                 Rutherford (rd)

It is the activity of amount of radioactive substance that undergoes 10⁶ disintegration per second.

It is denoted by rd.

1 rd        = 10¹⁰ dps = 10⁶Bq

Nuclear Transmutation:

·         The phenomenon of conversion of an element into another element artificially by bombarding the nuclei of any atom by projectile like α-rays (He), proton (₁H¹), neutron, deuterons etc. is known as nuclear transmutation.

Nuclear Reaction:

·         The phenomenon in which nucleus of an atom involves in change is known as nuclear reaction.

Example:

₉₂U²³⁵ + ₀H¹  à ₅₆Ba¹⁴⁰ + ₃₆Kr⁹³ + 3₀n¹ + Energy

Types of Nuclear Reaction

Nuclear Fusion:

The phenomenon in which two or more small nuclei unite together to form a heavy nucleus with evolution of huge amount of heat energy is known as nuclear fusion.

Example:

₁H² + ₁H³ à ₂He⁴ + ₀n¹

                                                                        Application of Nuclear Fusion:

i.                     Nuclear Fusion naturally occurs on the surface of stars and sun to produce heat and light.

ii.                   Nuclear fusion is applied to make nuclear weapons like hydrogen bomb.

Thermo-nuclear reaction:

The phenomenon in which two or more small nuclei unite together in presence of huge amount of heat energy to form a heavy nucleus is known as Thermo-nuclear fusion.

Example:

Nuclear fusion on the surface of the sun and stars.

                                Reaction:

                                ₁H¹ + ₁H¹  à ₁H² + e⁰

Nuclear Fission:

The phenomenon in which heavy nucleus is decomposed into two or more light nuclei by bombarding with a projectile like neutrons is knowns as nuclear fission.

Example:

₉₂U²³⁵ + ₀H¹  à ₅₆Ba¹⁴⁰ + ₃₆Kr⁹³ + 3₀n¹ + Energy

Types of Fission Reaction:

1.       Controlled nuclear fission reaction:

The nuclear fission which is controlled by reducing the speed of projectile like neutrons by adding moderator such as heavy water, graphite etc. on the path of projectile is called controlled nuclear fission.

Example:

Nuclear fission on the thermonuclear power plant

2.       Uncontrolled nuclear fission reaction:

The nuclear fission which is fission cannot be controlled by adding moderator on the path of projectile is called uncontrolled nuclear fission.

Example:

Nuclear fission in atomic bomb

                                                Application of Nuclear Fission:

i.                     It is used in thermonuclear power plant to produce huge amount of heat energy.

ii.                   It is used to making weapons like atom bomb.

S. No.	Nuclear Fusion	Nuclear Fission
1.	The phenomenon in which two or more small nuclei unite together to form a heavy nucleus with evolution of huge amount of heat energy is known as nuclear fusion	The phenomenon in which heavy nucleus is decomposed into two or more light nuclei by bombarding with a projectile like neutrons is knowns as nuclear fission.
2.	It is not a chain reaction.	It is a chain reaction.
3.	The product form is non-radioactive.	The product form is radioactive.
4.	Less amount of energy is liberated.
5.	It is impossible to control.	It can be controlled.
6.	Example: Nuclear fusion on the surface of the sun and stars.	Example: Nuclear fission in atomic bomb

 

 

Radioactive Isotopes:

·         The different radioactive atoms of an element having different unstable nuclei but same atomic number are called radioactive isotopes.

Example:

Isotopes of Uranium: ₉₂U²³⁵, ₉₂U²³⁸

Isotopes of Thorium: ₉₀Th²³⁴, ₉₀Th²³³

Application Of Radioactivity:

1.       Industrial Field:

i.         Thickness of a material can be determined by placing a radioactive source on one side of the material and counting device on other side.

ii. When a single pipeline is used to transfer more than one petroleum product a small amount of radioactive isotope is placed in a last portion of one substance to signal it’s end and to start another.

2.       Medical field:

Different types of radioactive isotopes are used to cure various disease on the medical field such as:

a.       Cobalt 60 is used to cure cancer.

b.       Gold 192 is used to cure blood cancer.

c.       Fe-59 is used to study deficiency of RBC

 

3.       Geological Dating:

Age of rocks, earth, fossil is determined by carbon dating process by using mass ratio of ₆C¹⁴ and ₆C¹² present in sample.

Isotope ₆C¹⁴ is a radioactive, so it is spontaneously disintegration in the dead body and decay parts of animals and plants which helps to determine half-life period of rocks, earth, fossils.

               

Difference Between Nuclear Reaction and Chemical Reaction:

S. No.	Nuclear Reaction	Chemical Reaction
1.	Nucleus is involved in this reaction	Valance electron are involved in this reaction.
2.	There is no breaking and formation of bond.	Certain bond is broken down and formed.
3.	It produces huge amount heat energy.	It cannot produce huge amount of heat energy.
4.	Reaction is irreversible.	The reaction may be reversible or irreversible.
5.	They always produce new element.	it produces compound as well as element.
6.	It needs high temperature for initiation.	It doesn’t need or needs low temperature for initiation.