Home Science Nuclear Chemistry

Radioactive Isotopes

Definition, Examples, Uses

Radioactive Isotopes of Lead, Uranium, Thorium

Radioactive isotopes or radioisotopes also called a radionuclide, or radioactive nuclide of any chemical element have the same atomic number (electron) but different in masses numbers due to varying numbers of the neutron particles inside nuclei. The radioisotopes are unstable and spontaneous decay the radioactive subatomic particles like alpha, beta, and gamma in form of energy. The stable radioactive isotopes in learning chemistry possess identical properties and chemical reactions because of their identical electronic configuration but the radioactive properties of isotopes that depend on the nucleus are different. Radioactive isotopes of lead, uranium, thorium, iodine, sodium, and cobalt used by researchers in radioactive medicine in radiotherapy, biological chemistry, agricultural chemistry, trace chemical analysis, and radioactive nuclear power generation process.

But most of the examples, the radioactive isotopes or radioisotope uses mainly in radiotherapy for cancer treatment or used as the electromagnetic spectrum radiation in medicine, analytical chemistry, and application of age determination of hydrocarbon or carbon compounds or mineral. Continuous emission of alpha, beta, and gamma rays from radioisotopes of uranium and thorium, form the most stable radioactive isotopes of lead. This process forming the list of radioactive decay series or chain of radioactive isotopes in nuclear physics and chemistry.

Radioactive isotopes or radioisotopes Lead, Uranium, and Thorium in decay series and uses in medicine and chemical analysis


Radioactive Emission of Alpha and Beta Rays

The emission of alpha rays within the radioactive atoms loses two units of atomic number and four units of mass number. For example, if a radioactive isotope having mass number = M and atomic number = Z. Therefore, after the emission of the alpha particle, the atomic and mass number of newborn radioactive isotope = (Z – 2) and (M – 4) respectively. But for the emission of beta rays from the nucleus of radioactive isotope increases the atomic number by one unit and mass numbers remain unchanged. For example, when an element ejected a beta ray the atomic number of newborn radioisotope = (Z + 1).

Group Displacement Law and Radioactive Isotopes

In 1913 Soddy define the law of radioactivity to describe the position of the radioactive isotopes or radioisotopes in the periodic table known as group displacement law state as, When an alpha particle emitted in a radioactive decay step, the product displaced two places to the left in the periodic table but the radiation of beta particles results in a displacement of the product to one place to the right.

The year when Soddy proposes the definition of displacement law for radioactive isotopes or radioisotopes of the periodic table elements, the knowledge of the atomic structure or electronic orbital configuration was still incomplete. He proposes this definition by extensive chemical studies on the disintegration products of different radioisotopes. Soddy define the term isotopes for such radioactive elements occupying the same position in the periodic table.

Decay Series of Radioisotopes

Uranium is the first discovered radioactive f-block elements with atomic number 92. Since uranium-238 successive decay to form the most stable radioisotopes of lead-208 is an example of radioactive decay series. Hence the mother element along with all the daughter elements converted to the stable radioactive isotope of lead. This series of disintegration is called the radioactive decay series.

Radioactive Decay of Uranium-238 to Lead-206

Unstable radioisotopes of uranium-238 decay to form the most stable radioactive isotope of lead-206. Therefore, the entire route involves eight alpha and six beta emission. The mass number of all the decay products given by 4n +2 (n = 59 for uranium-238). Therefore, these series are known as 4n +2 series ( n = an integer).

Uranium-235 Decay Series

Radioisotopes of uranium-235 or (4n+3) series start with uranium-235 and ends with lead – 207. Therefore, seven alpha and four beta radiate in the entire route of radioactive emission.

Thorium-232 Decay Series

Unstable radioactive isotopes of thorium-232 undergo successive decay to form the most stable radioactive isotopes of lead with mass number 208. Therefore, the entire decay chain of thorium-232 involves six alpha and four beta emission. This is the 4n radioactive decay series.

Analytical and Medicinal Uses

A list of radioactive isotopes of hydrogen, carbon, oxygen, nitrogen, sodium, cobalt, iodine, sulfur, etc is very much used in different disciples like research, medicine, agriculture, biology, trace analysis, and analytical problems. The uses of radioactive isotopes or radioisotopes may be classified into the following types like chemical analysis, medicine uses, for the determination of the age, and agricultural analysis to detected fertilizer like sulphuric acid, nitric acid, phosphate fertilizer.

Radioactive Isotopes in Chemical Analysis

Radioactive isotopes have played a key role in the evaluation of the chemical kinetics reaction mechanism in organic chemistry test. Hence the mechanism of esterification is easily evaluated by using an oxygen isotope. Therefore, the process of esterification has two possible mechanisms. First carboxylic acid OH may react with the hydrogen atom of the alcohol to eliminate water. The second alcohol OH reacts carboxylic hydrogen of acid.

Hydrolysis of ester carried out with water labeled by O-18 (radioisotope) indicates that after hydrolysis O-18 formed acid solution in the reaction. A study with radioactive isotope like sulfur-35 has been using to establish the non-equivalency of the two sulfur atoms in thiosulfate ion. All the iodine in HgI4 ion is equivalent proved by studies with radioisotopes of iodine.

Uses of Radioactive Isotopes in Medicine

Radiation therapy of radioactive isotopes uses mainly as a weapon to kill the diseased tissue in the human body in our daily life. It involves either external or internal sources of spectrum radiation.  Radioactive molecule and nuclear radiation produce during nuclear reactions affect our environmental pollution.

Radioactive isotope like cobalt-60 is an example of a gamma emitter with definite wavelengths uses in radiation therapy for inhibits the Millicent tissue or treatment of cancer in medicine. A radioactive isotope of iodine-131 uses in external radiation therapy for the treatment and diagnosis of thyroid glands in the human body. Radioisotope of sodium-24 isotopes uses in the abnormality of the blood circulation in the human body. Therefore, the doctor injected the vein of the patient with sodium salt containing sodium-24 isotope. Radioisotope like Phosphorus-32 uses in leukemia therapy. Leukemia is the overproduction of white blood cells in the human body.

The radioactive isotopes or radioisotopes in atomic chemistry uses mainly in trace chemical analysis (a trace amount of isotope mixed with a stable non-radioisotopes), radiotherapy in medicine, and agricultural fertilizer analysis. But naturally occurring radioactive isotopes or radioisotopes of uranium, thorium, and lead of our environment uses mainly in the electric energy generation process for mankind.