Isobars and Isotopes

Updated on

An element which differs in chemical properties, but has similar physical properties is known as an isobar. In short, isobars are elements which have different atomic numbers, but the same mass number. They will display different chemical properties because of the difference in electron count. An isobar will contain the same atomic mass but a different atomic number due to the added number of neutrons which recompense the number of nucleons.

Nickel and Iron are examples of two isobars. While they both have the same mass number i.e. 58, the atomic number of nickel and iron is 28 and 26 respectively.

Consider an example of two things which are similar in color and physical appearance, it should be difficult to distinguish between them. However, as we measure the weight of these two, we will find a difference. The isotopes concept can be related to this example.

We all know that each atom is made of electrons, protons, and neutrons. Electrons revolve around the nucleus that is made of protons and neutrons. Atomic mass is the sum of a few protons and the number of neutrons. Atomic number is equivalent to the number of protons. While the number of protons is always the same in an element, the number of neutrons keeps on altering. 

Atoms in which the number of neutrons differ from each other, while the number of protons remain the same are known as isotopes. Basically, elements which have similar atomic numbers, but different mass numbers are known as isotopes.

Examples of Isobars

  • The mass number of the atoms of potassium, argon, and calcium is 40.
  • 19K40, 18Ar40, 20Ca40. 19, 18, 20 which are represented as the subscripts are the atomic numbers of the three elements respectively (isobars). Their chemical properties vary with changing atomic numbers.

Examples of Isotopes

  • Protium, deuterium, and tritium are the 3 isotopes of hydrogen. 
  • They have the same number of protons, but they differ in the number of neutrons.
  • The number of neutrons is 0 in protium; it is 1 in deuterium; meanwhile the number of neutrons is 2 in tritium.

Difference Between Isotopes and Isobars

  • While isobars are chemical elements that have the same mass, isotopes are different atomic structures of the same element.
  • Physical properties of isobars are mostly similar. On the other hand, isotopes tend to have different physical properties.
  • While isobars have equal atomic masses, isotopes have different atomic masses.
  • The chemical elements of isobars are different. The chemical elements of the isotopes are the same, but in different forms. 
  • While Isobars have different atomic numbers, isotopes have the same atomic numbers.

Uses of Isotopes

Medical Field

  • Gamma rays emitted from cobalt-60 can be used in radiotherapy (cancer treatment).
  • Less penetrating radiation from strontium-90 or phosphorus-32 is used for treating superficial cancers like skin cancer.
  • Heart pacemaker uses plutonium-238 for regulating patients’ heartbeats.
  • Iodine-131 is used for treatment of thyroid disease.
  • Carbon-14 is used for estimating the age of fossils.


  • Phosphate fertilizer containing phosphorus-32 is used in agriculture.
  • Radioactive tracer studies using carbon-14 have helped us in understanding protein synthesis and photosynthesis better.

Industrial Sector

  • Sodium-24 is used for tracing gas/oil pipe leaks.
  • Radiation from krypton-85 is used for regulating the thickness of plastic sheets.
  • Gamma rays by Cobalt-60 are passed through food for destroying the bacteria, which otherwise would spoil the food.

Uses of Isobars

  • Nuclear reactors make use of uranium isobars.
  • Isobars of iodine are used for treatment of goiter.
  • Isobars of cobalt are used for cancer treatment. 

In this article, we have discussed about isotopes and isobars.  

Check Your Knowledge

Isobars are elements which have different atomic numbers, but the same mass number. 

 Nickel and Iron.

Elements which have similar atomic numbers, but different mass numbers are known as isotopes.


Leave a Reply

Your email address will not be published. Required fields are marked *