Question 3 — The composition of the nuclei - Questions at the end of the chapter - Chapter 8 - Journey Inside the Atom (Exploration)

Last updated at July 3, 2026 by

Question 3
The composition of the nuclei of three atomic species X, Y, and Z are given as follows.
Nucleus X Y Z
Number of protons 18 17 17
Number of neutrons 19 18 20
Explain the relation between the following: (i) Y and Z (ii) Z and X.
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  • X: Z=18, A=18+19=37.   Y: Z=17, A=17+18=35.   Z: Z=17, A=17+20=37.
  • (i) Y and Z — both have 17 protons (same atomic number) but different mass numbers (35 and 37) → they are isotopes .
  • (ii) Z and X — different atomic numbers (17 and 18) but the same mass number (37) → they are isobars .
Same A versus Same Z Same protons means isotopes Same mass number means isobars
Back to: 8.9.2 Isobars
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