Question 11 — An atom 70X has 31 - Questions at the end of the chapter - Chapter 8 - Journey Inside the Atom (Exploration)

Last updated at July 16, 2026 by

Question 11
An atom ⁷⁰X has 31 electrons. How many neutrons are there in its nucleus?
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  • Electrons = protons = 31 (neutral atom), so Z = 31.
  • Mass number A = 70.
  • Neutrons = A − Z = 70 − 31 = 39 .
Finding Neutrons
Neutrons equal mass number minus protons; protons equal electrons for a neutral atom.
Back to: 8.6 Mass Number
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