The original nucleus was protactinium with atomic mass 231 and atomic number before the radioactive decay.
<h2>
What is radioactive decay?</h2>
Radioactive decay is the process in which unstable atomic nucleus loses energy through radiation. A substance that has unstable nuclei is said to be a radioactive substance. Alpha decay, beta decay, and gamma decay are three of the most frequent kinds of decay, and they all entail the emission of one or more particles.
Here,
211 po or polonium 211 has 84 protons.
5 alpha emission means +20 amu and +10 protons,
3 beta emission means -0 amu and -3 protons,
So,
Atomic mass(A) = 211 + 20 - 0 = 231
Atomic Number(Z) = 84 + 10 - 3 = 91
Therefore, Atomic mass 231 and atomic number 91 represent the nucleus protactinium.
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