An atomic physicist determines that an atom is composed of 8 positively charged particles and has a mass of 15 amu. Which is the best conclusion that can be drawn?

The 8 positively charged particles are protons. An atom’s mass in amu is approximately the total number of protons and neutrons, so 15 − 8 = 7 neutrons. Therefore, the best conclusion is that the atom has 7 neutrons and 8 protons.

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