Chemistryhard · Past Paper
A neutral atom of an element has 2, 8, 8, 1 configuration. How many neutrons are in its isotope with mass 40?
A19
B21
C20
D39
✓ Correct Answer: B — 21
Total electrons = 19 (Potassium). Neutrons = Mass (40) - Atomic Number (19) = 21.
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