Isotopes and Isobars

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What are Isobars?

Isobar is an element that differs in the chemical property, but it has similar physical property. Hence, we can say that isobars are the elements that have a different atomic number but with the same mass number. Also, they have a different chemical property because there is a difference in the electron count. An isobar contains the same atomic mass but a different atomic number because an added number of neutrons recompense the number of nucleons.

An example of two Isotopes and Isobars is nickel and iron. These both have the same mass number, which is 58, whereas the atomic number of nickel is 28, and the atomic number of iron is 26.

Example of Isobar

Potassium, Argon, and calcium contain atoms of the same mass number 40.

19K40, 18Ar40, 20Ca40, where 19, 18, 20 represented as subscripts are the atomic numbers of the 3 elements respectively, are the isobars. Because the atomic numbers vary, their chemical properties also vary. The structure of potassium, argon, and calcium is represented below.

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What are Isotopes?

Let us consider an example of 2 things, which appear to be the same in colour, in the physical appearance, such that we cannot distinguish between them. However, when we measure the weight of these two, then we find a difference. We can relate the isotopes concept with this example.

As we all know that every atom is made of electrons, protons, and neutrons. Whereas the nucleus is made of only protons and neutrons, but the electrons revolve around the nucleus. Atomic mass can be defined as the sum of a few protons and the number of neutrons. Moreover, the atomic number is equal to the number of protons. The number of protons is always the same In an element, but the number of neutrons keeps on changing.

Isotopes are the atoms, where, the number of neutrons differs from each other, and the number of protons remains the same. From the definition of atomic mass and the atomic number, which is given above, we can conclude that isotopes are the elements that have a similar atomic number with different mass numbers.

Let us understand something about the isotopes of hydrogen.

  • There are 3 isotopes of hydrogen: protium, deuterium, and tritium. 

  • All these have the same number of protons, but they differ in the number of neutrons.

  • In protium, the number of neutrons is 0; in deuterium, it is 1; in tritium, the number of neutrons is 2.

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Let us look at the difference between isotopes and isobars, as tabulated below.

Difference Between Isotopes and Isobars



These are the chemical elements, that have the same mass.

These are the different atomic structures of the same element.

The physical properties are often similar.

In general, there are different physical properties.

These have equal atomic masses.

These have different atomic masses.

Their chemical elements are different.

Their chemical elements are the same but in different forms.

They have different atomic numbers.

They contain the same atomic numbers.

Uses of Isotopes

Uses of Isotopes in Medicine

  • Gamma-rays that are emitted from cobalt-60 can be used in radiotherapy for cancer treatment.

  • Superficial cancers like skin cancer are treated by less penetrating radiation from the strontium-90 or phosphorus-32.

  • A heart pacemaker that contains plutonium-238 can be used to regulate the patients’ heartbeats with heart problems.

  • Iodine-131 can also be used in thyroid disease treatment.

  • Carbon-14 is used to estimate the bone’s age, fossils, or wood by measuring the fraction of carbon-14 that it contains.

Isotope Uses in Agriculture

  • The phosphate and metabolism uptake of phosphorus by plants is studied using a phosphate fertilizer that contains phosphorus-32.

  • Furthermore, the radioactive tracer studies by using carbon -14 have helped understand protein synthesis and photosynthesis.

IIsotope Uses in the Industry

  • Sodium-24 is used to trace the gas or oil pipe leaks and ventilating systems.

  • Radiation from krypton-85 is used to control the plastic sheet thickness in the industry.

  • Cobalt-60’s gamma rays are passed through food to destroy the bacteria, which causes food to spoil without changing the flavour, quality, or texture of the food.

Uses of Isobars

Let us look at a few uses of isobars:

  • Nuclear reactors can use the uranium’s isobars

  • Iodine’s Isobars are used in goitre treatment

  • For cancer treatment, isobars of cobalt can be used

FAQs (Frequently Asked Questions)

Q1. Explain the Importance of Isobar Chemistry?

Ans. Atmospheric pressure differs according to location, even if it is at the same altitude. Isobars give reference lines running accompanying a path, where the pressure is the same along the line. With a series of lines, every marking places where the pressures have similar specified value, which is a map - user can get a reasonable estimate at any map location either by reading the line’s pressure if it happens to pass through the interesting location exactly or by the interpolation depending on the nearest isobars, which is the one at a higher pressure compared to the interesting location and the isobar nearest, with lower pressure.

They are in effect to an approximate method, which is a three-dimensional graph on a two-dimensional surface.

Q2. Why the Elements Have Isobars and Isotopes?

Ans. Because of the presence of a different number of neutrons in atoms of the same element, it contains different isotopes. Different elements can have different isobars due to the same mass number (s) of neutrons, protons.

Q3. How Do the Isotopes Form?

Ans. Atoms that hold an equal proton number but with a different number of protons and neutrons are called isotopes.

Q4. Explain Isotopes and Isobars with Examples?

Ans. Isotopes contain the same number of protons but with a varied number of neutrons. The pneumonic can be given as “isotopes contain the same number of Protons.” Therefore, carbon-12, carbon-13, carbon-14, carbon-15 are the isotopes.

The isobars contain the same number of nucleons or the atomic mass, but they have different numbers of protons and neutrons. The pneumonic can be given as “isobars have a similar Atomic mass.” Therefore, boron-12, oxygen-12, nitrogen-12, and carbon-12 are isobars.