Isotopes and Isobars
Isotopes are atoms of the same element with the same atomic number but different mass numbers. Isobars are atoms of different elements with the same mass number but different atomic numbers.
Practice This ConceptMain explanation
Teacher explanation
Isotopes have the same number of protons but different numbers of neutrons. Therefore, they are the same element but differ in mass number. Isobars have the same mass number but different proton numbers, so they are different elements.
Example
Carbon-12 and carbon-14 are isotopes. Argon-40 and calcium-40 are isobars.
Simple analogy
IsoTOPES: same proton number; isoBARS: same big mass number.
Common confusion
Students often say isotopes have different atomic numbers, but isotopes have the same atomic number.
Exam tip
For isotopes, check same Z. For isobars, check same A.
Answer writing and exam use
1-mark use
Write the exact meaning of isotopes and isobars in one clean line.
2-mark use
Define isotopes and isobars and add one example or condition.
3-mark use
Explain isotopes and isobars, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
Open the concept quiz intro first, review the test details, and then start a focused MCQ set from this concept only. Instant score and answer review are live now.
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