# Can you write the nuclear decay equation for the beta decay of iodine-131?

Aug 20, 2014

The equation is $\text{_53^131"I" → ""_54^131"Xe" + color(white)(l)_text(-1)^0"e}$

#### Explanation:

β decay is a process in which a nucleus emits an electron.

The nuclear symbol for a β particle is ${\textcolor{w h i t e}{l}}_{\textrm{- 1}}^{0} \text{e}$.

In any nuclear equation, the sum of the subscripts (atomic numbers, $\text{Z}$) and the sum of the superscripts (atomic masses, $\text{M}$) must be equal on each side of the equation.

For the β decay of iodine 131, we have

$\text{_53^131"I" → color(white)(l)_text(Z)^"M""X" + color(white)(l)_text(-1)^0"e}$

Hence

$131 = \text{M} + 0$, so $\text{M} = 131$
$53 = \text{Z - 1}$, so $\text{Z} = 53 + 1 = 54$

The element $\text{X}$ with $\text{Z = 54}$ is $\text{Xe}$.

So the equation is

$\text{_53^131"I" → ""_54^131"Xe" + color(white)(l)_text(-1)^0"e}$

Note that in β decay, the product has the same mass number but an atomic number that has increased by 1.

Here's a video on writing β decay equations.