Determine the identity of the daughter nuclide from the alpha decay of Rn.

Question

Determine the identity of the daughter nuclide from the alpha decay of  Rn.

Quizplus · Accepted Answer

In alpha decay, an alpha particle (which is a helium nucleus with two protons and two neutrons) is emitted from the parent nucleus, causing the atomic number to decrease by 2 and the mass number to decrease by 4. 
11ea6923_1855_cf6b_80d0_572f65096a23_TB6105_11 Rn has a mass number of 219 (the number after the underscore), and an atomic number of 86 (the number of protons, which is the second digit from the end).
After alpha decay, the mass number will be 215 (219-4) and the atomic number will be 84 (86-2), which corresponds to element Po, choice A.

Determine the Identity of the Daughter Nuclide from the Alpha