The symbol for a radioactive nuclide is 90234Th Which statement is correct?

In nuclide notation, the lower number is the atomic number, which equals the number of protons. For ²³⁴₉₀Th, the atomic number is 90, so the correct statement is that the nuclide’s atomic number is 90. Its mass number is 234, and it has 234 − 90 = 144 neutrons.

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