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

The equation is ##""_53^131"I" → ""_54^131"Xe" + color(white)(l)_text(-1)^0"e"##

is a process in which a nucleus emits an electron.

The nuclear symbol for a β particle is ##color(white)(l)_text(-1)^0"e"##.

In any nuclear equation, the sum of the subscripts (atomic numbers, ##"Z"##) and the sum of the superscripts (atomic masses, ##"M"##) must be equal on each side of the equation.

For the β decay of iodine 131, we have

##""_53^131"I" → color(white)(l)_text(Z)^"M""X" + color(white)(l)_text(-1)^0"e"##

Hence

##131 = "M" + 0##, so ##"M" = 131## ##53 = "Z - 1"##, so ##"Z" = 53 + 1 = 54##

The element ##"X"## with ##"Z = 54"## is ##"Xe"##.

So the equation is

##""_53^131"I" → ""_54^131"Xe" + color(white)(l)_text(-1)^0"e"##

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

Here's a video on writing β decay equations.