Question

How do you write a balanced nuclear equation for alpha decay of Po-218?

Answer 1

Here's how you can do that.

Explanation:

When a radioactive nuclide undergoes alpha decay, it emits an alpha particle, `""_2^4alpha`, which is essentially the nucleus of a helium-4 atom.

This means that after the alpha particle is emitted

• the mass number of the nuclide will decrease by `4` `->` this happens because the alpha particle contains `2` protons and `2` neutrons
• the atomic number of the nuclide will decrease by `2` `->` this happens because the alpha particle contains `2` protons

You can thus say that you have

`""_ (color(white)(.)84)^218"Po" -> ""_ (color(white)(.)(84-2))^((218 - 4))"X" + ""_ 2^4alpha`

A quick look in the Periodic Table of Elements will show that the element that has the atomic number equal to

`84 - 2 = 82 ->` conservation of charge

is lead, `"Pb"`. This means that the resulting nuclide will be lead-214 since its mass number is equal to

`218 - 4 = 214 ->` conservation of mass

The balanced nuclear equation that describes the alpha decay of polonium-218 will look like this

`""_ (color(white)(.)84)^218"Po" -> ""_ (color(white)(.)82)^214"X" + ""_ 2^4alpha`

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