Question

Uranium (U) has a mass number of 238 and an atomic number of 92 and decays by emission of an alpha particle. The product of this decay is (Points : 5)

A.) uranium (U), with a mass number of 234 and an atomic number of 92.

B.) lead (Pb), with a mass number of 234 and an atomic number of 91.

C.) thorium (Th), with a mass number of 234 and an atomic number of 90.

D.) radium (Ra), with a mass number of 234 and an atomic number of 88.

E.) thorium (Th), with a mass number of 234 and an atomic number of 91.

Answer 1

Remember that in balancing the nuclear reaction ,

the sum of the atomic numbers of the reactants is equal to the sum of the atomic numbers of the products.

also the sum of the atomic masses of the reactants is equal to the sum of the atomic masses of the products.

₉₂U²³⁸₉₀Th²³⁴ + ₂He⁴

                               ( alpha particle)

So the Product is thorium (Th), with a mass number of 234 and an atomic number of 90.

Therefore option (C) is correct