# When U-238 transmutates into Th-234, what does this represent?

Apr 20, 2018

$\text{_(92)^(238) "U" -> ""_(90)^(234)"Th" + ""_2^4 "He}$

#### Explanation:

an alpha particle has a form identical to a helium nucleus.
it contains $2$ neutrons and $2$ protons.

the mass number of an atom is its number of protons added to its number of neutrons.

the numbers $238$ and $234$ show the mass number of each isotope.

it can also be found that the mass number of an alpha particle is $2 + 2$, which is $4$.

releasing an alpha particle from an atom would decrease its mass number by $4$.

$238 - 234 = 4$

here, the mass number decreases by $4$ in the decay process. this means that the decay was of an alpha particle.