Identify the nuclide produced when uranium-238 decays by alpha emission: 238 92u→42he + ?

Alpha decay is an emission of a ₂⁴He nucleus. After an alpha decay, the formed daughter nuclide has the reduced mass number by 4 and reduced atomic number by 2 with compared to the parent atom.

After an alpha decay of ₉₂²³⁸U, the formed daughter atom should be Th (Thorium) which has atomic number as 92 - 2 = 90. The equation is,

₉₂²³⁸U → ₉₀²²⁹Th + ₂⁴He

The sum of mass number and sum of atomic number should be equal in both side.

the correct answer would be b. amelia, because the particals of gas move really fast (charged particals) and gas also has a lot of room (particals move independently) so the only answer that has both of those is amelia's.