A radioactive nuclide is used to detect eye tumors. An atom of this radionuclide contains 15 protons, 15 electrons, and 17 neutrons. Which is symbol of this radionuclide?

The atomic number equals the number of protons, so this nuclide has atomic number 15. Its mass number is protons plus neutrons: 15 + 17 = 32. The isotope symbol is therefore ³²₁₅P, which is choice A, phosphorus-32.

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