In the decay reaction 235 U --> X + 4 He, what element represents X?

In the decay reaction provided, where uranium-235 (235 U) decays to produce another element and helium-4 (4 He), it is important to apply the principles of nuclear reactions and isotopic notation.

In a decay process, the sum of the atomic numbers and the sum of the mass numbers on both sides of the equation must be equal due to the conservation of mass and charge.

Starting with uranium-235, the atomic number is 92, and the mass number is 235. The product of the decay process includes a helium-4 atom, which has an atomic number of 2 and a mass number of 4. To find the unknown element, denoted as X, we can use these conservation laws.

1. Mass Number Conservation:

• The initial mass number of 235 must equal the mass number of X plus the mass number of helium.

• 235 = mass number of X + 4

• This simplifies to mass number of X = 235 - 4 = 231.

2. Atomic Number Conservation:

• The initial atomic number of 92 must equal the atomic number of X plus the atomic number of helium.

• 92 = atomic number