The decay product represented by X : Thorium (Th) : ²³⁴₉₀Th
Further explanation
Given
Decay reaction
²³⁸₉₂U ⇒ ⁴₂He + X
Required
The decay product
Solution
Radioactivity is the process of unstable isotopes to stable isotopes by decay, by emitting certain particles,
- alpha α particles ₂He⁴
- beta β ₋₁e⁰ particles
- gamma particles ₀γ⁰
- positron particles ₁e⁰
- neutron ₀n¹
In a decay reaction, the sum of the mass number and atomic number of the elements in the reactants and products must be the same
So the mass number of the element X = 238 - 4 = 234
Atomic number of the element X = 92 - 2 = 90
If we look at the periodic system, then the element with atomic number 90 is Thorium (Th)