Hey guys in this new video, we’re going to take look at Alpha Decay.
So, remember Rutherford talked about the 3 major types of decays.
There’s alpha decay, beta decay and gamma emission.
Here, we have alpha decay.
We’re going to say alpha decay occurs when unstable nucleus emits a particle composed
of 2 protons and 2 neutrons.
Now, just think about it, we say that our atomic mass equals the number of protons plus
the number of neutrons.
So here our atomic mass is, we lose 2 protons and 2 neutrons.
So, 2 plus 2 gives me 4.
Atomic Mass = number of protons + number of neutrons = 2 + 2 = 4
Your atomic mass is protons and neutrons added and your atomic number is just the number
of protons.
So, the number of protons loss is 2.
Atomic number = number of protons = 2 So, we’re going to say the alpha particle
is represented by 4 for your atomic mass over 2 your atomic number and here we have our
alpha symbol α. 24 α
Now we can also say that on our periodic table, we have an element that also has as atomic
mass of 4 and an atomic number of 2.
That element is Helium, 24He.
So, we can say that the alpha particle can also be represented by the element Helium
because Helium has the same atomic mass as an alpha particle and has the same atomic
number as an alpha particle.
And remember, we’re using the term decay.
So, decay means that this alpha particle will be our product.
So if you want to take a look at an example of this, we can think of for examples on your
periodic table.
You could have Polonium which in your periodic table is Po.
Polonium, we’re going to say let’s talk about isotope 210.
Polonium (Po) – 210 Now, remember what these nuclear reactions.
They can happen with different isotopes of an element.
So, on your periodic table we’ll be doing different types of decays with different types
of isotopes.
So, don’t worry if your atomic mass on your periodic table doesn’t match my atomic mass.
That’s because I am dealing with a certain isotope of that element.
Remember, isotopes have the same atomic number, so they’re the same element, but they have
different number of neutrons, so we have different atomic masses.
So, here Polonium 210 means the atomic mass is 210Po.
If you look on your periodic table, Polonium has an atomic number, number of protons, of
84.
84210Po Now, we’re going to undergo alpha decay.
Alpha decay means we’re going to spit out or emit an alpha particle.
You can represent it like this 24 α or like this 24He.
Here I’ll just choose to show it as Helium.
So, we’re going to emit 4 over 2 Helium.
84210Po  24He Now, nuclear reactions are different from
regular reactions, but there are some similarities.
Just like you have to have a regular chemical reaction balanced, you have to have a nuclear
reaction also balanced.
So, here our total atomic mass is 210.
Here we have already an atomic mass of 4.
So, we need to create an element that when I added to the 4 gives me back this mass of
210.
So, the new element has to be 206 because 206 + 4 gives me 210.
Also, your atomic numbers need to match on both sides.
This atomic numbers 2, we need it to add up to 84.
So, it say that the new element would have to have 82 because 82 + 2 gives me 84.
And what element would that be?
Well that would be lead.
So, what we’d say here is that we’d say the alpha decay of 210Polonium creates a brand
new element 206Lead.
84210Po  24He + 82206Pb The Helium were the alpha particles that just
something that we emit, that’s just waste.
The new element that we’re concerned with is the Lead 206.
So, this represents an alpha decay, and it’s as simple as that.
Make sure that your atomic masses add up on both sides.
Make sure your atomic numbers add up on your both sides.