An atom contains 70 protons, 70 electrons, and 99 neutrons. What is the mass number?
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"A 5.00 L sample of helium at STP expands to 15.0 L. What is the new pressure on the gas?"
1 Answer
Apr 2, 2016
Explanation:
Mass number is number of protons + neutrons in the nucleus.
Since it has atomic number
