Isotopes and Isobars

What are Isotopes?

Let us take an example of two things which have the same color, same physical appearance, such that you cannot distinguish between these two. But when you measure the weight of these two things then you find that it is different. You can relate the concepts of isotopes with this example.

Isotopes and Isobars

As we all know that atoms are made up of electrons, protons, and neutrons. The nucleus is made up of protons and neutrons and the electrons revolve around the nucleus. Atomic mass is the sum of some protons and the number of neutrons and atomic number is equal to the number of protons. In an element, the number of protons is always the same, but the number of neutrons keeps on changing.

Isotopes are the atoms in which the number of neutrons differs and the number of protons is the same. From the above definition of atomic mass and the atomic number, we can conclude that isotopes are those elements having a same atomic number and different mass number.

Let us know something about the isotopes of hydrogen: There are three isotopes of hydrogen and these are protium, deuterium, and tritium. All three of them have a same number of protons, but the numbers in neutrons differ. In protium the number of neutrons is zero, in deuterium, it is one and in tritium, the number of neutrons is two.

What are Isobars?

Isobars are those elements which differ in the chemical property but have same physical property. So, we can say that isobars are those elements which have a different atomic number but the same mass number. Their chemical property is different because there is the difference in the number of electrons. It has the same atomic mass but different atomic no. Because an additional number of neutrons compensates the difference in the number of nucleons.

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

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Practise This Question

In Niels Bohr model of the atom, the orbits or shells are represented by the letters and numbers. Identify the correct statement.