Difference Between Isotopes and Isobars

In Class 9 Science (Structure of the Atom), atoms are classified based on their Atomic Number (Z) and Mass Number (A). The two most common classifications are Isotopes and Isobars. Let's understand the difference.

Question (Click to Flip)

What are isotopes and isobars?

Answer

Isotopes are atoms of the same element with the same atomic number but different mass numbers (like C-12 and C-14). Isobars are atoms of different elements with different atomic numbers but the same mass number (like Argon-40 and Calcium-40).

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Key Facts

Isotopes: Same Atomic Number, Different Mass Number. (Belong to the same element).

Isobars: Different Atomic Number, Same Mass Number. (Belong to different elements).

Memory Trick: Iso'topes' = 'P' for same Protons. Iso'bars' = 'A' for same Atomic Mass.

1. Isotopes (Same Element, Different Mass)

Definition: Isotopes are atoms of the same element that have the same atomic number but different mass numbers.
Why does it happen? They have the same number of protons and electrons, but a different number of neutrons inside the nucleus.
Chemical Properties: Because they have the same number of electrons, their chemical properties are exactly the same.
Examples of Isotopes:
- Hydrogen has 3 isotopes: Protium (Mass 1), Deuterium (Mass 2), and Tritium (Mass 3).
- Carbon has isotopes: C-12 and C-14.

2. Isobars (Different Elements, Same Mass)

Definition: Isobars are atoms of different elements that have different atomic numbers but the same mass number.
Why does it happen? They have a different number of protons, but the total sum of protons and neutrons in their nucleus happens to be the same.
Chemical Properties: Because they are entirely different elements, their chemical properties are completely different.
Example of Isobars:
- Argon (Atomic Number 18) and Calcium (Atomic Number 20). Even though they are different elements, they both have a mass number of 40.

Questions and Answers

What are isotopes and isobars?+

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