# Question #1292d

##### 1 Answer

Here's what I got.

#### Explanation:

The idea here is that when a radioactive nuclide undergoes **beta-minus decay**, its **atomic number** will **increase** by **mass number** will remain unchanged.

In beta-minus decay, a neutron located inside the nucleus is converted to a proton, which is what causes the **atomic number** to increase by **beta particle**,

So if you take

#""_ 19^40"K" -> ""_ Z^A"X" + ""_ (-1)^(color(white)(-)0)"e" + ""_ 0^0bar(nu)_"e"#

Now, in every nuclear reaction, mass and charge **must be conserved**. This means that you have

#40 = A + 0 + 0 " " -># conservation of mass

#19 = Z + (-1) + 0 " " -># conservation of charge

Solve these two equations to get

This means that you have

#""_Z^A"X" = ""_20^40"Ca"#

The balanced nuclear equation that describes the beta-minus decay of potassium-40 looks like this

#""_ 19^40"K" -> ""_ 20^40"Ca" + ""_ (-1)^(color(white)(-)0)"e" + ""_ 0^0 bar(nu)_"e"#