Answer:
Po - 206
Explanation:
Think about the nuclear equation for the alpha decay of Po - 210. Po - 210 has 84 protons and 126 neutrons in it's nucleus, and an alpha particle is identical to a helium - 4 nucleus, meaning it is present with 2 protons and 2 neutrons.
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Knowing that, during the alpha decay, Po - 210 will form a daughter nucleus identical to a polonium - 210 present with 4 less of it's atomic mass ( number of protons and neutrons ), and 2 less of it's atomic number ( number of protons ). Why? Because Po - 210 will split into this daughter nucleus and an alpha particle.
Po - 210 has an atomic mass of 210 and an atomic number of 84. It's daughter nucleus will have an atomic mass of 206, and an atomic number of 82, Po - 206.
Hope that helps!
