In the next set of boxes, enter the mass number and atomic number of the alpha particle, which has the same composition as the nucleus of a helium (He) atom. After filling in the
boxes in the Gizmo, what is the atomic mass of the first element?
New mass number
238
U
+
92
New atomic number

234

Explanation:

From the question given above, the following data were obtained:

Alpha particle => ⁴₂He

²³⁸₉₂U —> ? + ⁴₂He

Let the unknown be ⁿₓZ. Thus, the equation becomes

²³⁸₉₂U —> ⁿₓZ + ⁴₂He

Next, we shall determine x, y and Z. This can be obtained as follow:

92 = x + 2

Collect like terms

92 – 2 = x

90 = x

x = 90

238 = n + 4

Collect like terms

238 – 4 = n

234 = n

n = 234

ⁿₓZ => ²³⁴₉₀Z => ²³⁴₉₀Th

Thus the balanced equation

²³⁸₉₂U —> ²³⁴₉₀Th + ⁴₂He

Therefore, the atomic mass of the first element is 234