# How do you complete the following alpha decay reaction?

##### 1 Answer

Jul 2, 2016

#### Explanation:

The general notation of a nuclide (

In wich

In alpha decay the nucleus emits a particle that contains 2 protons and 2 neutrons, which is similar to the nucleus of helium. So a notation for the nuclide (

Now you can complete the equation given in the example:

The last step is finding the nuclide that has 90 protons and 142 neutrons in a table of nuclides. This appears to be **Thorium ( #Th#)**.

This makes the equation complete: