Question

When U-238 transmutates into Th-234, this represents _______.

Alpha decay
Electron capture
Beta-decay
Gamma decay

Answer 1

A: Alpha decay.

Step-by-step explanation:

The transmutation of ²³⁸U is a nuclear reaction that yields ²³⁴Th and an alpha particle.

Now, Alpha decay is a radioactive decay whereby an atomic nucleus emits an alpha particle which then changes into an atom with a mass number that is decreased by four and atomic number decreased by 2.

In this case, mass number is reduced from 238 to 234. Thus, it's an alpha decay.