The table below gives the numbers of protons, electrons, and neutrons in four atoms.AtomNumber of protonsNumber of electronsNumber of neutrons1393952240405033939544404051Based on the information that is given, which atom in the table has the highest mass?

An atom’s mass is determined mainly by its protons and neutrons; electrons contribute very little. Adding protons and neutrons gives atom 1: 39 + 52 = 91, atom 2: 40 + 50 = 90, atom 3: 39 + 54 = 93, and atom 4: 40 + 51 = 91. Atom 3 has the highest total, so the correct choice is C, atom 3.

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