Nuclear Chemistry

Radioactivity is the process by which the atoms of a naturally occurring substance emit particles or radiation due to the spontaneous disintegration of their atomic nuclei.

Types of Radiation

1. Alpha (α) particles
2. Beta (β) particles
3. Gamma (γ) rays

Types of Radioactive Decay

Alpha Decay

In alpha decay, the nucleus emits an alpha particle, made up of two protons and two neutrons (like a helium nucleus). Alpha particles have high energy but very low penetration—they can be blocked by a sheet of paper or the outer layer of skin.

Beta Decay

In beta decay, a beta particle—an electron with either a negative or positive charge—is emitted from the nucleus. Beta particles can travel several meters in air and a few millimeters into the body. Thin materials like aluminium or plastic can stop them.

Gamma Decay

Gamma decay occurs when the nucleus releases excess energy by emitting a high-energy photon, known as a gamma ray. Gamma rays travel at the speed of light and require dense materials like lead, steel, or thick concrete for shielding.

Comparison of Radiation Types

Advantages of Radioactive Substances

1. It is used in medical treatments, such as treating malignant growths similar to X-rays.
2. Serves as the primary source of nuclear fuel for energy generation.
3. Radioactive isotopes are useful in tracer techniques.
4. Help in estimating the age of archaeological findings.

Disadvantages of Radioactive Substances

1. Radiation exposure destroys living tissue cells.
2. Can disrupt chemical reactions in blood cells, potentially leading to fatal consequences.

Artificial Radioactivity

Artificial radioactivity occurs when an element becomes radioactive through exposure to radiation, such as neutron irradiation. This process can happen either accidentally or intentionally.

Examples of Artificial Radioactivity Reactions

• Reaction 1:
  \[\alpha_{2}^{4} + N_{7}^{14} \rightarrow F_{9}^{18} \rightarrow O_{8}^{17} + H_{1}^{1} + \text{energy}\]
• Reaction 2:
  \[\alpha_{2}^{4} + Al_{13}^{27} \rightarrow P_{15}^{30} + n_{0}^{1} \rightarrow Si_{14}^{30} + e_{1}^{0} + \text{energy}\]
• Reaction 3:
  \[n_{0}^{1} + Li_{3}^{6} \rightarrow H_{1}^{3} + He_{2}^{4} + \text{energy}\]
• Reaction 4:
  \[n_{0}^{1} + Mg_{11}^{24} \rightarrow Na_{11}^{24} + P_{1}^{1} + \text{energy}\]
• Reaction 5:
  \[\alpha_{2}^{4} + Be_{4}^{9} \rightarrow C_{6}^{12} + n_{0}^{1} + \text{energy}\]
• Reaction 6:
  \[n_{0}^{1} + Co_{27}^{59} \rightarrow Co_{27}^{60} + \text{energy}\]

Artificially Produced Isotopes

Isotopes can also be produced artificially by bombarding elements with neutrons, protons, or deuterons. Examples include:

• Reaction 7:
  \[S_{10}^{34} + n_{0}^{1} \rightarrow S_{10}^{35} + \text{energy}\]
• Reaction 8:
  \[Br_{35}^{79} + n_{0}^{1} \rightarrow Br_{35}^{80} + \text{energy}\]

Radioisotopes

Artificially produced isotopes are often unstable and decay by emitting alpha (\(\alpha\)), beta (\(\beta\)), or gamma (\(\gamma\)) radiation. These unstable isotopes are known as radioisotopes. They are created through neutron, proton, or deuteron bombardment of elements.

Half-Life

The half-life (\( T_{1/2} \)) of a radioactive element is the time taken for half of its atoms to decay. The SI unit is seconds (s). It is given by:

\[ T_{1/2} = \frac{\ln 2}{\lambda} = \frac{0.693}{\lambda} \]

Binding Energy

Binding energy is the energy required to split an atomic nucleus. It is given by the equation:

\[ E = \Delta m C^2 \]

Where:

• \( E \) = Energy (Joules)
• \( \Delta m \) = Mass defect (kg)
• \( C \) = Speed of light (m/s)

Nuclear Fusion

Nuclear fusion is the process where two or more light nuclei combine to form a heavier nucleus, releasing a significant amount of energy. An example of fusion is:

\[ ^2_1H + ^1_0n \rightarrow ^4_2He + n + \text{Energy} \]

Nuclear Fission

Nuclear fission occurs when a heavy atomic nucleus splits into two nearly equal parts, releasing a large amount of energy and additional neutrons. An example is:

\[ ^{235}_{92}U + ^1_0n \rightarrow ^{141}_{56}Ba + ^{92}_{36}Kr + 3(^1_0n) \]

Hydrogen Bomb and the Source of the Sun's Energy

Hydrogen Bomb

A hydrogen bomb contains heavy isotopes of hydrogen known as deuterium and tritium, along with lithium-6.

When an atomic bomb is detonated, its fission reaction generates intense heat. This heat rapidly raises the temperature of deuterium and tritium to about 10⁷°C within microseconds. At such a high temperature, fusion reactions between deuterium and tritium occur, releasing a massive amount of energy and causing the hydrogen bomb to explode.

Lithium-6 plays a crucial role in producing additional tritium required for the fusion process. When bombarded by neutrons (produced during fusion), lithium-6 breaks down into tritium and helium.

The energy source of a hydrogen bomb is similar to that of the sun, as both rely on nuclear fusion. However, while the sun's energy supports life, the hydrogen bomb’s energy is destructive.

Source of the Sun's Energy

The sun functions as a massive thermonuclear reactor where hydrogen atoms are continuously fused into helium atoms. During this fusion, some mass is lost and converted into energy.

The key reaction in the sun is the fusion of four hydrogen nuclei into a single helium nucleus. The energy released from this process is emitted in the form of heat and light, which sustains life on Earth. Similarly, stars also generate their energy from hydrogen fusion.

Comparison of Nuclear Fission and Nuclear Fusion

Advantages & Disadvantages of Nuclear Energy

Advantages of Nuclear Energy

1. It produces a large amount of energy from a very small amount of nuclear fuel.
2. It does not produce greenhouse gases like carbon dioxide.
3. It provides a reliable and continuous source of energy, operating 24 hours a day for years.
4. It does not produce smoke or air pollutants.

Disadvantages of Nuclear Energy

1. Although inexpensive to operate, nuclear power plants are extremely costly to build.
2. Disposing of nuclear waste is difficult, dangerous, and expensive.
3. Nuclear facilities can be targets for terrorist attacks, and the uranium used can be converted into weapons.
4. There is always a risk of accidents, which can release harmful radioactive materials into the environment, causing serious harm to living organisms.