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 ₉₂ ²³⁸U, 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.