What is Radioactivity?
Unstable atomic nuclei do not have intense binding energy due to the overload of neutrons and protons, thus exhibiting radioactivity. These particles emit electromagnetic energy due to nuclear instability. Radiation is emitted in several radioactive decays including alpha, beta, and gamma. Radioactivity causes loss of energy, causing further instability, an increase in the size of the nucleus, and concentrated mass.
Radioactivity Definition Chemistry
Radioactivity in chemistry can be defined as a phenomenon that deals with the spontaneous emission of radioactive particles causing the nuclear reaction. In the phenomenon of radioactivity, the unstable atomic nucleus loses significant energy and is processed under three heads, namely, alpha-beta and gamma.
(Image to be added soon)
The image illustrates the penetration of alpha, beta and gamma particles through paper, lead and aluminium. Alpha particles are stopped by the paper sheet, beta particles are stopped by the aluminium sheet whereas gamma particles successfully penetrated through lead.
Alpha Decay And Its Occurrence
Alpha decay is a significant type of radioactive decay in which the unstable nuclei of the atom can emit alpha particles to get converted into a stable element. The alpha particle has two protons, i.e. subatomic positive ions and neutrons, i.e. two subatomic neutrally charged ions. These subatomic particles have their configuration ratio altered in the process of radioactivity causing characteristic changes. The mass number is altered and reduced by four, whereas the atomic number is reduced by two. The radiation caused by the alpha particles is hazardous for human health, and in case inhaled or ingested it can lead to lung cancer. There are only a handful of elements that can undergo alpha decay since it requires the nucleus of the element to be unstable and large to withstand the fission changes. The alpha particles have a five percent speed of light, and the energy level varies around 5MeV. The alpha particles have a positive charge since there are no electrons in the shell; thus, the particles have a mass. The absence of electrons leads the alpha particle to vigorously react with the matter in the environment through which it loses its energy. The heavy particles because the radioactive decay process reacts with the human body, heavy enough to harm the body tissues. At times, the overdose leads to blisters and burns.
Uses Of Radioactivity
Radioactive particles have scores of applications in several fields outside nuclear weaponry.
Medicine
Radioactive isotopes have extensive use in diagnosis and therapy which work as effective tracers. In hospital settings, X-Ray, PET, and CT scan machines are used to diagnose and monitor medical conditions. Radionuclides are used to treat cancers, thyroid, and hyperthyroidism. Significant radioactive tracers are used to trace cardiac stress with the help of Technetium-99. The isotope can be used to identify arteries and areas near the heart, which are resulting in blood flow to diminish. Radiography involves using radioactive particles to detect structural anomalies and irregularities in the basic bone structure.
Industrial
Strong radiations are used to root out the presence of toxic and dangerous pollutants released by the power plants in the lush environment. The agricultural industry uses this phenomenon for controlling the breeding of insects and exposing the radiation to make hybrid plants. Engineers use radioactive particles to measure moisture in soil profiles, fluid levels in liquids, construction material and detect defects in the welding and casting process of metal.
Effects Of Radioactive Energy On Human Health
Radioactive radiation can cause both long term and short term effects on the human body. It is completely dependent on the dose of radiation which comes in contact with the body
Radiation poisoning can cause nausea and organ damage to lymph nodes and bone marrow.
Strong radiation levels can cause haemorrhage and skin peeling, which at times can even lead to death. When the human body is vulnerable to high doses in a short period, the damage done is acute. The radioactive radiation kills significant cells in the human body, and it takes a long span to recover the damage done. At times, the body can be penetrated with radiation in case of the infected food chain, inhalation and indigestion, causing long term health effects. The alpha decay particles are absorbed by the human body, causing danger to health. The isotopes undergo beta-decay of the iodine element can cause thyroid cancer, and the absorbed dose is enough for causing death.
Did You Know?
Radon is the first radioactive isotope that proposed lung cancer in humans, and the radium decays affected the German miners in 1913.
FAQs on Radioactivity Alpha Decay
1. What is alpha decay and how does it occur in radioactive elements?
Alpha decay is a type of radioactive disintegration where an unstable atomic nucleus emits an alpha particle to become more stable. An alpha particle is identical to a helium nucleus, containing two protons and two neutrons. This process occurs primarily in very heavy elements, like Uranium or Radium, because their large nuclei are held together less tightly due to strong electrostatic repulsion between protons. By ejecting an alpha particle, the nucleus reduces its size and becomes a new element with a lower atomic number and mass number.
2. What is the general equation that represents alpha decay?
The general equation for a parent nucleus (X) undergoing alpha decay to form a daughter nucleus (Y) is written as:
AZX → A-4Z-2Y + 42He
Here, A represents the mass number and Z represents the atomic number. As you can see, in alpha decay, the mass number of the parent nucleus decreases by 4, and the atomic number decreases by 2. The energy released in the process, known as the Q-value, is carried away as the kinetic energy of the daughter nucleus and the alpha particle.
3. Can you provide a common example of alpha decay, like that of Uranium-238?
A classic example of alpha decay is the disintegration of Uranium-238 (U-238) into Thorium-234 (Th-234). The nuclear equation for this decay is:
23892U → 23490Th + 42He
In this reaction, the Uranium-238 nucleus (with 92 protons and 146 neutrons) emits an alpha particle, transforming into a Thorium-234 nucleus (with 90 protons and 144 neutrons).
4. How does alpha decay differ from beta and gamma decay?
Alpha, beta, and gamma decay are all processes through which an unstable nucleus releases energy, but they differ significantly:
- Particle Emitted: Alpha decay emits a helium nucleus (2 protons, 2 neutrons). Beta decay emits an electron or a positron. Gamma decay emits a high-energy photon (electromagnetic radiation).
- Change in Nucleus: Alpha decay reduces the mass number by 4 and atomic number by 2. Beta decay changes the atomic number by +1 or -1 but leaves the mass number unchanged. Gamma decay does not change the mass number or atomic number; it only lowers the energy state of the nucleus.
- Penetrating Power: Alpha particles have the lowest penetrating power and can be stopped by paper. Beta particles are more penetrating but can be stopped by a thin sheet of aluminium. Gamma rays are highly penetrating and require thick lead or concrete to be stopped.
5. Why do only very heavy nuclei typically undergo alpha decay?
Alpha decay is most common in heavy nuclei (those with an atomic number greater than 82) because of the interplay between two fundamental forces. The strong nuclear force holds protons and neutrons together, but it is very short-ranged. In large nuclei, the long-range electrostatic repulsion between the many positively charged protons becomes significant and starts to overwhelm the strong force. Emitting an alpha particle is an energetically favourable way for these massive, unstable nuclei to reduce this repulsion and move to a more stable, lower-energy state. Lighter nuclei are generally stable or decay through other means like beta decay.
6. What are the key properties of an alpha particle?
An alpha particle has several distinct properties:
- Composition: It is a helium nucleus, consisting of two protons and two neutrons.
- Charge: It has a positive charge of +2e.
- Mass: It has a relatively large mass, approximately four times the mass of a proton.
- Ionising Power: Due to its large mass and double positive charge, it has a very high ionising power, meaning it readily knocks electrons off atoms it passes.
- Penetrating Power: It has very low penetrating power and can be stopped by a few centimetres of air or a single sheet of paper.
- Velocity: Alpha particles are emitted with high velocities, typically around 5% of the speed of light.
7. How can alpha particles be harmful to human health if they can be stopped by a sheet of paper?
This is a crucial distinction between external and internal exposure. Externally, the dead outer layer of skin is sufficient to block alpha particles, making external alpha-emitting sources relatively safe. However, the danger arises if an alpha-emitting substance is inhaled, ingested, or enters the body through a wound. Inside the body, there is no protective layer. Because of their high ionising power, they can deposit a large amount of energy in a very small area, causing significant damage to living cells and DNA. This localised damage can lead to an increased risk of cancer, particularly lung cancer if an alpha-emitter like Radon gas is inhaled.
8. What is the significance of Gamow's theory in explaining alpha decay?
Gamow's theory was a groundbreaking application of quantum mechanics to nuclear physics. Classically, an alpha particle does not have enough energy to overcome the strong nuclear force's potential barrier and escape the nucleus. Gamow's theory explained this phenomenon using quantum tunnelling. It proposes that the alpha particle has a small but non-zero probability of 'tunnelling' through this energy barrier, even without having the energy to overcome it classically. This theory successfully explained the vast range of half-lives observed for alpha emitters and correctly related the half-life to the energy of the emitted alpha particle.
