Question

The element X has an atomic mass number of 238 and an atomic number
of 92. It emits an alpha particle forming an element y. Y can be represented
by

Options

• 234 x 90

• 236 x 90

• 235 x 91

• 238 x 92

• 238 x 934

Answer 1

Initially element is represented by ₉₂x²³⁸
a particle is represented by ₂He⁴ this means it contains 2 protons and 2
neutrons so mass of a particle is 4 unit. Thus after emitting a particle mass
number of element would decrease by 4 unit and atomic number of element would decrease by 2.
So after emitting a particle ₉₂x²³⁸ would become _{92 - 2} x ^23a-4 = ₉₀ x ²³⁴ .

_bQ^a = ₉₃p²³⁹
So answer is A.
.