Science
Mass number
In Class 9 Science, the topic Mass Number introduces how the nucleus is described through the total number of protons and neutrons in an atom. Students learn the notation A, distinguish mass number from atomic number, and understand that electrons are not included in this count. The concept helps them read atomic symbols, compare atoms of the same element, and identify isotopes such as carbon-12 and carbon-14 in the chapter Journey Inside the Atom.
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Practice questions are not available for this topic yet. We plan to add questions with clear explanations soon. You can keep practising other topics in the meantime.
- Class / subject
- 9 · Science
- Chapter
- Journey Inside the Atom
- Topic
- Mass number
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