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Radioactive Isotopes

Last Updated : 19 Dec, 2023
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Radioactive Isotopes or Radioisotopes are the isotopes of the elements that are not stable, i.e. they emit some radiation and change the composition of their nucleus. Radioactive isotopes are defined as the isotopes of any chemical element that have different masses and unstable nuclei and release energy by spontaneously emitting radiation in the form of alpha rays, beta rays, and gamma rays. This property of some nuclei to emit energy as alpha, beta, and gamma rays is called radioactivity, and the isotopes of the elements that show radioactivity are called radioisotopes or radioactive isotopes.

In this article, we will learn about Isotope definition, Radioactive Isotopes, Uses of Radioactive Isotopes, and others in detail.

Isotopes Definition

Isotopes are variations of an element that have the same number of protons but differ in the number of neutrons in the atom. These isotopes have some different properties as compared to normal atoms, for example, the atom with higher numbers of neutrons in the atom has higher weight. There are two categories of the isotopes that are,

  • Stable Isotopes
  • Radioactive Isotopes

Learn More, Isotopes

The isotopes that do not emit energy from their nucleus are called stable isotopes and the isotopes of the elements that emit energy from the nucleus are called radioactive isotopes. For example, in case of isotopes of hydrogen,

  • Protium (1H1) and Deutarion(1H2) are stable isotopes.
  • Tritium (1H3) is unstable or radioactive isotopes.

The image added below shows the isotopes of the hydrogen,


Radioactive Isotopes Definition

Isotopes of the atom exhibiting radioactivity are called Radioactive isotopes or Radioisotopes. In radioisotopes their nucleus have a higher number of neutrons that tends to be unstable and to maintain its stability these nucleus emit in form of apha, beta, and gama rays, these rays are called radioactive rays and this phenomenon is called Radioactivity.

Radioactivity is the property of some elements and not all the elements shows radioactivity. The rate at which the radioactive isotopes emits radioactive rays is expressed in terms of its half-life. Half-life of an radioactive element is defined as the time taken by one half of all the radioactive nucleus to decay.

Radioactive Isotopes Examples

Various Examples of radioactive isotopes of elements are,

  • Carbon-14
  • Technetium-99
  • Thallium-204
  • Cobalt-60
  • Iridium-192
  • Cadmium-109, etc.

Are All Isotopes Radioactive?

In short the answer to above question is, No, not all isotopes are not radioactive. There are several isotopes of the elements that are stable and does not exhibit radioactivity. Only the isotopes in which the number of nuetrons to the number of protons in the nucleus goes above a certain threshold exhibit radioactivity.

Laws of Radioactivity

Various laws that controls the radioactivity of an element are added below,

  • Rate of decay of the radioactive nucleus is independent of the temperature and pressure.
  • Radioactivity follows the law of conservation of charge.
  • In radioactivity the rays that are emitted by the radioactive material is, alpha rays, beta rays, and gamma rays.
  • Rate of decay of radioactive element is proportional to the number of atoms that are prsest in the given sample.

Uses of Radioactive Isotopes

radioactive Isotopes have a variety of uses and vrious uses of radioactive isotopes of the elements are added below,

Uses of Radioactive Isotopes in Medicine

Cobalt-60 is a radiation source used in cancer treatment to decrease the growth of the disease. Other radioactive isotopes are used as tracers in metabolic research and diagnostics. Carbon-14 is used in a breath test to detect the ulcer-causing bacteria Helicobacter pylori.

Uses of Radioactive Isotopes in Industry

In industry, radioactive isotopes are used to determine the thickness of metal or plastic sheets, with the strength of the radiations that penetrate the substance being studied revealing the precise thickness. They can also be used to generate modest amounts of electricity. One example is the use of Plutonium-238 in spacecraft.

Other uses of the radioactive isotopes are,

  • D2O (D denotes deuterium) is called heavy water and is used as a neutron moderator in nuclear reactors.
  • Carbon-14 is also radioactive and is used in carbon dating (carbon dating is an archaeological technique of determining the age of fossils).

Various uses of some radioactive isotopes are added in the table added below,





312 Days

It track heavy metals from mining waste


5 Years

It is used to sterlize equipments


10 Years

Uses in Indicator lights of appliance.


12 Days

Used in testing of pollutant levels


74 Days

Used in Metal Radiography

What is Radioactivity?

Radioactivity is a nuclear phenomenon in which there is a spontaneous emission of radiations from the nuclei of atoms during their decay. The atom generally decays and energy is released in the form of alpha, beta and gamma radiations. 

In 1896 it was Sir Henry Becquerel who discovered the phenomenon of radioactivity. In a dark room once he left a uranium salt was placed on a photographic plate wrapped in black paper. Some days later when he investigated, he was surprised to found that the photographic plate had been affected. Later on, the same observation was made with the other salts of uranium. 

From these observations, he concluded that uranium and the number of its salts by themselves emit some kind of radiation that can pass through the cover (i.e. black paper, glass or wood, etc.) of the outside the photographic plate and affect it. These radiations were called the Becquerel rays. Later renamed as alpha, beta and gamma rays.

Types of Radioactivity

The radioactive substances emit three types of radiations as stated earlier, due to the imbalance and instability in their atoms due to the varying number of neutron

Alpha Rays or Alpha Decay

These are positively charged beams of particles, or precisely helium nuclei (4He2). When the number of neutrons is more than that of the proton, the excessive neutron converts into a proton and in this process an alpha particle is released, Generally observed for elements heavier than lead. This results in decreasing in Mass number A and Atomic Number Z.

Beta Rays or Beta Decay

These are negatively charged streams of particles. When an unstable nucleus contains neutrons more than the protons, a neutron may change into a proton by emitting an electron. The electron given out from the nucleus at a high speed is called a beta particle. This result is increasing in atomic number and no change in the mass number.

Gamma Rays

Gamma rays are fast-moving streams of uncharged particles. Sometimes after alpha or beta emission is found to be followed by the Gamma-emission. It occurs when the daughter or the parent nucleus is in a state of excitation (i.e. it has an excess of energy). This extra energy is released in the form of electromagnetic radiation known as gamma-radiation (or y-ray photon). The gamma-ray is massless and has no electric charge this implies, no neutrons or protons are lost, hence the nucleus does not decay into a different nucleus, i.e, there is no change in the mass number A and atomic number Z of the nucleus in gamma emission.

Conditions for Isotopes to Show Radioactivity

In isotopes the number of neutrons is greater than the original atom, which adds excessive mass, Due to excessive mass, the nuclei get unstable and henceforth nucleus releases energy in form of radioactivity. The isotopes have an unstable combination of neutrons and protons or excess energy in their nucleus. are called radioactive isotopes

Examples of natural radioisotopes are Uranium-235 (about 99.3% Uranium is radioactive in nature, only 0.7% is Uranium 238). Examples of artificially created radioisotopes are Fluorine-18 and Molybdenum-99.

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Radioactive Isotopes-FAQs

1. What is meant by Radioactive Isotopes?

Radioactive Isotopes are also called radioisotope, they are isotopes of the elements that shows radioactivity.

2. What are 4 Examples of Radioactive Isotopes?

Four examples of radoactive isotopes are,

  • Carbon-14
  • Strontium-85
  • Nickel-63
  • Iodine-131

3. What is Radioactivity?

Radioactivity is the property of element that allows some nucleus with higher number of neutrons to emeit alpha, beta, and gamma rays. The isotopes that shows radioactivity are called radioactive isotopes.

4. What are the Three Types of Radioactivity?

The three types of radioactivity are,

  • Alpha Decay
  • Beta Decay
  • Gamma Rays

5. Is Uranium-235 a Radioisotope?

Uranium-235 (U-235) is the radioactive isotopes of the element Uranium. In nucleus of Uranium it have 92 Protons, and 143 Neutrons.

6. Which substance was the first to be detected radioactive?

Uranium was the first radioactive substance to be detected. It has three isotopes, U-238 (most abundant), U-235, U-234.

7. Which Isotope of Carbon is used in Carbon Dating?

Carbon-14 is used in carbon dating as it is the radioactive isotope of carbon. Carbon has three naturally occurring isotopes C-12, C-13, C-14.

8. What are Uses of Radioactive Isotopes?

Radioactive Isotopes have various uses and some of its uses are,

  • Radioactive isotopes are used in medice
  • Radioactive isotopes are used in industries.
  • Radioactive isotopes is used to for carbon-14 dating, etc.

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