0:00:00.000,0:00:00.690


0:00:00.690,0:00:03.660
SAL: Everything we've been[br]dealing with so far in our

0:00:03.660,0:00:06.410
journey through chemistry has[br]revolved around stability of

0:00:06.410,0:00:08.420
electrons and where electrons[br]would rather

0:00:08.420,0:00:10.340
be in stable shells.

0:00:10.340,0:00:14.030
And like all things in life,[br]if you explore the atom a

0:00:14.030,0:00:16.400
little further you'll realize[br]that electrons are not the

0:00:16.400,0:00:19.250
only stuff that's going[br]on in an atom.

0:00:19.250,0:00:24.250
That the nucleus itself has some[br]interactions, or has some

0:00:24.250,0:00:27.140
instability, that needs to[br]be relieved in some way.

0:00:27.140,0:00:28.740
That's what we'll talk[br]a little bit

0:00:28.740,0:00:31.420
about in this video.

0:00:31.420,0:00:35.110
And actually the mechanics of[br]it are well out of the scope

0:00:35.110,0:00:37.450
of a first-year chemistry[br]course, but it's good to at

0:00:37.450,0:00:39.570
least know that it occurs.

0:00:39.570,0:00:43.110
And one day when we study the[br]strong nuclear force, and

0:00:43.110,0:00:45.570
quantum physics, and all the[br]like, then we can start

0:00:45.570,0:00:49.280
talking about exactly why these[br]protons and neutrons,

0:00:49.280,0:00:52.810
and their constituent quarks[br]are interacting

0:00:52.810,0:00:53.530
the way they do.

0:00:53.530,0:00:55.500
But with that said, let's[br]at least think about the

0:00:55.500,0:01:00.890
different types of ways that a[br]nucleus can essentially decay.

0:01:00.890,0:01:03.880
So let's say I have a[br]bunch of protons.

0:01:03.880,0:01:06.830
I'll just draw a couple here.

0:01:06.830,0:01:09.590
Some protons there, and I'll[br]draw some neutrons.

0:01:09.590,0:01:13.430
And I'll draw them in[br]a neutral-ish color.

0:01:13.430,0:01:16.780
Maybe let me see, like a[br]grayish would be good.

0:01:16.780,0:01:21.520
So let me just draw some[br]neutrons here.

0:01:21.520,0:01:22.020
How many protons do I have?

0:01:22.020,0:01:24.300
I have 1, 2, 3, 4, 5, 6, 7, 8.

0:01:24.300,0:01:32.410
I'll do 1, 2, 3, 4, 5,[br]6, 7, 8, 9 neutrons.

0:01:32.410,0:01:34.870
And so let's say this is the[br]nucleus of our atom.

0:01:34.870,0:01:36.960
And remember-- and this is, you[br]know, in the very first

0:01:36.960,0:01:39.860
video I made about the atom--[br]the nucleus, if you actually

0:01:39.860,0:01:43.320
were to draw an actual atom--[br]and it's actually very hard to

0:01:43.320,0:01:45.440
drawn an atom because it has[br]no well-defined boundaries.

0:01:45.440,0:01:49.050
The electron really could be,[br]you know, at any given moment,

0:01:49.050,0:01:49.980
it could be anywhere.

0:01:49.980,0:01:52.740
But if you were to say, OK,[br]where is 90% of the time the

0:01:52.740,0:01:53.700
electron is going to be in?

0:01:53.700,0:01:55.680
You'd say, that's the radius,[br]or that's the

0:01:55.680,0:01:57.750
diameter of our atom.

0:01:57.750,0:02:00.530
We learned in that very first[br]video that the nucleus is

0:02:00.530,0:02:05.450
almost an infinitesimal portion[br]of the volume of this

0:02:05.450,0:02:08.340
sphere where the electron[br]will be 90% of the time.

0:02:08.340,0:02:12.080
And the neat takeaway there[br]was that, well, most of

0:02:12.080,0:02:15.280
whatever we look at in life[br]is just open free space.

0:02:15.280,0:02:17.030
All of this is just[br]open space.

0:02:17.030,0:02:19.400
But I just want to repeat[br]that because that little

0:02:19.400,0:02:23.660
infinitesimal spot that we[br]talked about before, where

0:02:23.660,0:02:26.320
even though it's a very small[br]part of the fraction of the

0:02:26.320,0:02:29.030
volume of an atom-- it's[br]actually almost all of its

0:02:29.030,0:02:31.890
mass-- that's what I'm zooming[br]out to this point here.

0:02:31.890,0:02:34.240
These aren't atoms, these[br]aren't electrons.

0:02:34.240,0:02:36.580
We're zoomed into the nucleus.

0:02:36.580,0:02:40.040
And so it turns out that[br]sometimes the nucleus is a

0:02:40.040,0:02:43.650
little bit unstable, and it[br]wants to get to a more stable

0:02:43.650,0:02:44.400
configuration.

0:02:44.400,0:02:46.600
We're not going to go into the[br]mechanics of exactly what

0:02:46.600,0:02:48.700
defines an unstable nucleus[br]and all that.

0:02:48.700,0:02:51.880
But in order to get into a[br]more unstable nucleus,

0:02:51.880,0:02:55.820
sometimes it emits what's called[br]an alpha particle, or

0:02:55.820,0:02:58.470
this is called alpha decay.

0:02:58.470,0:03:04.440
Alpha decay.

0:03:04.440,0:03:06.220
And it emits an alpha particle,

0:03:06.220,0:03:09.160
which sounds very fancy.

0:03:09.160,0:03:12.450
It's just a collection of[br]neutrons and protons.

0:03:12.450,0:03:16.690
So an alpha particle is two[br]neutrons and two protons.

0:03:16.690,0:03:20.850
So maybe these guys, they just[br]didn't feel like they'd fit in

0:03:20.850,0:03:25.110
just right, so they're a[br]collection right here.

0:03:25.110,0:03:27.740
And they get emitted.

0:03:27.740,0:03:30.070
They leave the nucleus.

0:03:30.070,0:03:33.870
So let's just think what[br]happens to an atom when

0:03:33.870,0:03:36.050
something like that happens.

0:03:36.050,0:03:38.500
So let's just say I have some[br]random element, I'll just call

0:03:38.500,0:03:40.310
it element E.

0:03:40.310,0:03:43.020
Let's say it has p, protons.

0:03:43.020,0:03:45.660
Actually let me do it in the[br]color of my protons.

0:03:45.660,0:03:47.800
It has p, protons.

0:03:47.800,0:03:51.550
And then it has its atomic mass[br]number, is the number of

0:03:51.550,0:03:55.510
protons plus the number[br]of neutrons.

0:03:55.510,0:03:59.480
And do the neutrons[br]in gray, right?

0:03:59.480,0:04:06.590
So when it experiences[br]alpha decay, what

0:04:06.590,0:04:08.180
happens to the element?

0:04:08.180,0:04:11.890
Well, its protons are going[br]to decrease by two.

0:04:11.890,0:04:16.040
So its protons are going[br]to be p minus 2.

0:04:16.040,0:04:19.450
And then its neutrons are also[br]going to decrease by two.

0:04:19.450,0:04:21.320
So its mass number's going[br]to decrease by four.

0:04:21.320,0:04:27.100
So up here you'll have p minus[br]2, plus our neutrons minus 2,

0:04:27.100,0:04:28.940
so we're going to[br]have minus 4.

0:04:28.940,0:04:31.080
So your mass is going to[br]decrease by four, and you're

0:04:31.080,0:04:32.700
actually going to turn[br]to a new element.

0:04:32.700,0:04:34.710
Remember, your elements[br]were defined by

0:04:34.710,0:04:36.250
the number of protons.

0:04:36.250,0:04:40.630
So in this alpha decay, when[br]you're losing two neutrons and

0:04:40.630,0:04:43.300
two protons, but especially the[br]protons are going to make

0:04:43.300,0:04:44.460
you into a different element.

0:04:44.460,0:04:46.860
So if we call this element 1,[br]I'm just going to call it,

0:04:46.860,0:04:50.590
we're going to be a different[br]element now, element 2.

0:04:50.590,0:04:54.050
And if you think about what's[br]generated, we're emitting

0:04:54.050,0:04:58.600
something that has two protons,

0:04:58.600,0:05:00.340
and it has two neutrons.

0:05:00.340,0:05:02.740
So that its mass is going to be[br]the mass of the two protons

0:05:02.740,0:05:04.790
and two neutrons.

0:05:04.790,0:05:05.830
So what are we emitting?

0:05:05.830,0:05:09.810
We're emitting something that[br]has a mass of four.

0:05:09.810,0:05:12.170
So if you look at, what is two[br]protons and two neutrons?

0:05:12.170,0:05:14.740
I actually don't have the[br]periodic table on my

0:05:14.740,0:05:14.880
[? head. ?]

0:05:14.880,0:05:17.020
I forgot to cut and paste[br]it before this video.

0:05:17.020,0:05:19.680
But it doesn't take you long on[br]the periodic table to find

0:05:19.680,0:05:23.280
an element that has two protons,[br]and that's helium.

0:05:23.280,0:05:25.590
It actually has an atomic[br]mass of four.

0:05:25.590,0:05:29.390
So this is actually a helium[br]nucleus that gets emitted with

0:05:29.390,0:05:30.080
alpha decay.

0:05:30.080,0:05:31.875
This is actually a[br]helium nucleus.

0:05:31.875,0:05:35.010


0:05:35.010,0:05:39.170
And because it's a helium[br]nucleus and it has no

0:05:39.170,0:05:43.420
electrons to bounce off its two[br]protons, this would be a

0:05:43.420,0:05:44.950
helium ion.

0:05:44.950,0:05:48.490
So essentially it has[br]no electrons.

0:05:48.490,0:05:50.830
It has two protons so it[br]has a plus 2 charge.

0:05:50.830,0:05:53.350


0:05:53.350,0:05:59.110
So an alpha particle is really[br]just a helium ion, a plus 2

0:05:59.110,0:06:01.960
charged helium ion that is[br]spontaneously emitted by a

0:06:01.960,0:06:05.780
nucleus just to get to[br]a more stable state.

0:06:05.780,0:06:07.670
Now that's one type of decay.

0:06:07.670,0:06:08.850
Let's explore the other ones.

0:06:08.850,0:06:14.050
So let me draw another[br]nucleus here.

0:06:14.050,0:06:17.640
I'll draw some neutrons.

0:06:17.640,0:06:19.310
I'll just draw some protons.

0:06:19.310,0:06:24.200


0:06:24.200,0:06:27.920
So it turns out sometimes that[br]a neutron doesn't feel

0:06:27.920,0:06:30.710
comfortable with itself.

0:06:30.710,0:06:33.710
It looks at what the protons do[br]on a daily basis and says,

0:06:33.710,0:06:34.560
you know what?

0:06:34.560,0:06:37.780
For some reason when I look into[br]my heart, I feel like I

0:06:37.780,0:06:39.220
really should be a proton.

0:06:39.220,0:06:42.640
If I were a proton, the entire[br]nucleus would be a little bit

0:06:42.640,0:06:43.870
more stable.

0:06:43.870,0:06:46.860
And so what it does is, to[br]become a proton-- remember, a

0:06:46.860,0:06:49.180
neutron has neutral charge.

0:06:49.180,0:06:52.060
So what it does is, it[br]emits an electron.

0:06:52.060,0:06:54.070
And I know you're saying, Sal,[br]you know, that's crazy, I

0:06:54.070,0:06:55.760
didn't even know neutrons[br]had electrons in

0:06:55.760,0:06:56.900
them, and all of that.

0:06:56.900,0:06:58.050
And I agree with you.

0:06:58.050,0:06:58.810
It is crazy.

0:06:58.810,0:07:01.750
And one day we'll study[br]all of what exists

0:07:01.750,0:07:03.540
inside of the nucleus.

0:07:03.540,0:07:08.880
But let's just say that it[br]can emit an electron.

0:07:08.880,0:07:10.206
So this emits an electron.

0:07:10.206,0:07:12.730


0:07:12.730,0:07:15.460
And we signify that with its--[br]roughly its mass is zero.

0:07:15.460,0:07:17.830
We know an electron really[br]doesn't have a zero mass, but

0:07:17.830,0:07:19.970
we're talking about[br]atomic mass units.

0:07:19.970,0:07:25.130
If the proton is one, an[br]electron is 1/1,836 of that.

0:07:25.130,0:07:25.940
So we just round it.

0:07:25.940,0:07:27.250
We say it has a mass of zero.

0:07:27.250,0:07:29.380
Its mass really isn't zero.

0:07:29.380,0:07:32.670
And its charge is minus 1.

0:07:32.670,0:07:34.370
It's atomic, you can kind[br]of say its atomic

0:07:34.370,0:07:35.200
number's minus 1.

0:07:35.200,0:07:36.570
So it emits an electron.

0:07:36.570,0:07:39.760
And by emitting an electron,[br]instead of being neutral, now

0:07:39.760,0:07:41.020
it turns into a proton.

0:07:41.020,0:07:44.490


0:07:44.490,0:07:47.090
And so this is called[br]beta decay.

0:07:47.090,0:07:52.500


0:07:52.500,0:07:56.780
And a beta particle is really[br]just that emitted electron.

0:07:56.780,0:08:00.480
So let's go back to our little[br]case of an element.

0:08:00.480,0:08:03.940
It has some number of protons,[br]and then it has

0:08:03.940,0:08:05.980
some number of neutrons.

0:08:05.980,0:08:08.340
So you have the protons and[br]the neutrons, then you get

0:08:08.340,0:08:09.660
your mass number.

0:08:09.660,0:08:13.480
When it experiences beta[br]decay, what happens?

0:08:13.480,0:08:15.490
Well, are the protons changed?

0:08:15.490,0:08:18.890
Sure, we have one more proton[br]than we had before.

0:08:18.890,0:08:20.500
Because our neutron[br]changed into one.

0:08:20.500,0:08:23.410
So now our protons are plus 1.

0:08:23.410,0:08:25.186
Has our mass number changed?

0:08:25.186,0:08:26.720
Well let's see.

0:08:26.720,0:08:28.750
The neutrons goes down[br]by one but your

0:08:28.750,0:08:30.365
protons go up to by one.

0:08:30.365,0:08:32.380
So your mass number[br]will not change.

0:08:32.380,0:08:36.789
So it's still going[br]to be p plus N.

0:08:36.789,0:08:39.909
so your mass stays the same,[br]unlike the situation with

0:08:39.909,0:08:42.679
alpha decay, but your[br]element changes.

0:08:42.679,0:08:44.039
Your number of protons[br]changes.

0:08:44.039,0:08:47.975
So now, once again, you're[br]dealing with a new element in

0:08:47.975,0:08:49.470
beta decay.

0:08:49.470,0:08:52.530
Now, let's say we have[br]the other situation.

0:08:52.530,0:08:57.360
Let's say we have a situation[br]where one of these protons

0:08:57.360,0:09:00.750
looks at the neutrons and[br]says, you know what?

0:09:00.750,0:09:02.240
I see how they live.

0:09:02.240,0:09:04.170
It's very appealing to me.

0:09:04.170,0:09:13.910
I think I would fit in better,[br]and our community of particles

0:09:13.910,0:09:15.660
within the nucleus would[br]be happier if

0:09:15.660,0:09:17.160
I too were a neutron.

0:09:17.160,0:09:19.770
We'd all be in a more[br]stable condition.

0:09:19.770,0:09:23.660
So what they do is, that little[br]uncomfortable proton

0:09:23.660,0:09:27.340
has some probability of[br]emitting-- and now this is a

0:09:27.340,0:09:31.020
new idea to you-- a positron,[br]not a proton.

0:09:31.020,0:09:33.070
It emits a positron.

0:09:33.070,0:09:34.670
And what's a positron?

0:09:34.670,0:09:36.390
It's something that[br]has the exact

0:09:36.390,0:09:38.610
same mass as an electron.

0:09:38.610,0:09:42.890
So it's 1/1836 of the[br]mass of a proton.

0:09:42.890,0:09:46.200
But we just write a zero there[br]because in atomic mass units

0:09:46.200,0:09:47.830
it's pretty close to zero.

0:09:47.830,0:09:50.006
But it has a positive charge.

0:09:50.006,0:09:51.720
And it's a little confusing,[br]because they'll

0:09:51.720,0:09:52.630
still write e there.

0:09:52.630,0:09:54.440
Whenever I see an e, I[br]think an electron.

0:09:54.440,0:09:56.720
But no, they say e because it's[br]kind of like the same

0:09:56.720,0:09:59.500
type of particle, but instead[br]of having a negative charge,

0:09:59.500,0:10:00.830
it has a positive charge.

0:10:00.830,0:10:02.080
This is a positron.

0:10:02.080,0:10:04.980


0:10:04.980,0:10:08.450
And now we're starting to get[br]kind of exotic with the types

0:10:08.450,0:10:10.210
of particles and stuff[br]we're dealing with.

0:10:10.210,0:10:11.730
But this does happen.

0:10:11.730,0:10:15.920
And if you have a proton that[br]emits this particle, that

0:10:15.920,0:10:19.370
pretty much had all of its[br]positive charge going with it,

0:10:19.370,0:10:26.330
this proton turns[br]into a neutron.

0:10:26.330,0:10:29.160
And that is called positron[br]emission.

0:10:29.160,0:10:31.350
Positron emission is usually[br]pretty easy to figure out what

0:10:31.350,0:10:33.510
it is, because they call[br]it positron emission.

0:10:33.510,0:10:37.880
So if we start with the same E,[br]it has a certain number of

0:10:37.880,0:10:41.500
protons, and a certain[br]number of neutrons.

0:10:41.500,0:10:43.190
What's the new element[br]going to be?

0:10:43.190,0:10:46.060
Well it's going to lose[br]a proton. p minus 1.

0:10:46.060,0:10:47.770
And that's going to be turned[br]into a neutron.

0:10:47.770,0:10:49.620
So p is going to[br]go down by one.

0:10:49.620,0:10:51.030
N is going to go up by one.

0:10:51.030,0:10:55.020
So that the mass of the whole[br]atom isn't going to change.

0:10:55.020,0:10:57.550
So it's going to be p plus N.

0:10:57.550,0:11:00.500
But we're still going to have[br]a different element, right?

0:11:00.500,0:11:03.230
When we had beta decay,[br]we increased

0:11:03.230,0:11:04.150
the number of protons.

0:11:04.150,0:11:06.700
So we went, kind of, to the[br]right in the periodic table or

0:11:06.700,0:11:09.070
we increased our, well,[br]you get the idea.

0:11:09.070,0:11:12.440
When we do positron emission,[br]we decreased

0:11:12.440,0:11:14.700
our number of protons.

0:11:14.700,0:11:16.300
And actually I should[br]write that here in

0:11:16.300,0:11:17.510
both of these reactions.

0:11:17.510,0:11:20.460
So this is the positron[br]emission, and I'm left over

0:11:20.460,0:11:22.060
with one positron.

0:11:22.060,0:11:29.430
And in our beta decay, I'm left[br]over with one electron.

0:11:29.430,0:11:30.670
They're written the[br]exact same way.

0:11:30.670,0:11:32.660
You know this is an electron[br]because it's a minus 1 charge.

0:11:32.660,0:11:33.890
You know this is a positron[br]because it

0:11:33.890,0:11:35.810
has a plus 1 charge.

0:11:35.810,0:11:38.170
Now there's one last[br]type of decay that

0:11:38.170,0:11:39.140
you should know about.

0:11:39.140,0:11:42.810
But it doesn't change the number[br]of protons or neutrons

0:11:42.810,0:11:43.970
in a nucleus.

0:11:43.970,0:11:46.940
But it just releases a ton of[br]energy, or sometimes, you

0:11:46.940,0:11:48.350
know, a high-energy proton.

0:11:48.350,0:11:50.160
And that's called gamma decay.

0:11:50.160,0:11:52.510
And gamma decay means that these[br]guys just reconfigure

0:11:52.510,0:11:52.795
themselves.

0:11:52.795,0:11:54.460
Maybe they get a little[br]bit closer.

0:11:54.460,0:11:57.990
And by doing that they release[br]energy in the form of a very

0:11:57.990,0:12:03.180
high wavelength electromagnetic[br]wave. Which is

0:12:03.180,0:12:05.820
essentially a gamma, you could[br]either call it a gamma

0:12:05.820,0:12:08.230
particle or gamma ray.

0:12:08.230,0:12:09.450
And it's very high energy.

0:12:09.450,0:12:11.720
Gamma rays are something you[br]don't want to be around.

0:12:11.720,0:12:15.460
They're very likely[br]to maybe kill you.

0:12:15.460,0:12:17.130
Everything we did, I've said[br]is a little theoretical.

0:12:17.130,0:12:20.000
Let's do some actual problems,[br]and figure out what type of

0:12:20.000,0:12:21.750
decay we're dealing with.

0:12:21.750,0:12:24.400
So here I have 7-beryllium[br]where seven

0:12:24.400,0:12:26.900
is its atomic mass.

0:12:26.900,0:12:30.520
And I have it being converted[br]to 7-lithium So

0:12:30.520,0:12:31.440
what's going on here?

0:12:31.440,0:12:36.000
My beryllium, my nuclear mass[br]is staying the same, but I'm

0:12:36.000,0:12:42.240
going from four protons[br]to three protons.

0:12:42.240,0:12:45.130
So I'm reducing my number[br]of protons.

0:12:45.130,0:12:46.840
My overall mass hasn't[br]changed.

0:12:46.840,0:12:49.100
So it's definitely[br]not alpha decay.

0:12:49.100,0:12:50.960
Alpha decay was, you know,[br]you're releasing a whole

0:12:50.960,0:12:52.770
helium from the nucleus.

0:12:52.770,0:12:54.960
So what am I releasing?

0:12:54.960,0:12:57.410
I'm kind of releasing one[br]positive charge, or I'm

0:12:57.410,0:12:58.560
releasing a positron.

0:12:58.560,0:13:00.940
And actually I have this[br]here in this equation.

0:13:00.940,0:13:04.040
This is a positron.

0:13:04.040,0:13:07.140
So this type of decay of[br]7-beryllium to 7-lithium is

0:13:07.140,0:13:09.760
positron emission.

0:13:09.760,0:13:10.830
Fair enough.

0:13:10.830,0:13:12.400
Now let's look at[br]the next one.

0:13:12.400,0:13:19.870
We have uranium-238 decaying[br]to thorium-234.

0:13:19.870,0:13:25.140
And we see that the atomic mass[br]is decreasing by 4, minus

0:13:25.140,0:13:28.910
4, and you see that your atomic[br]numbers decrease, or

0:13:28.910,0:13:31.270
your protons are decreasing,[br]by 2.

0:13:31.270,0:13:33.810
So you must be releasing,[br]essentially, something that

0:13:33.810,0:13:37.390
has an atomic mass of four,[br]and a atomic number

0:13:37.390,0:13:39.680
of two, or a helium.

0:13:39.680,0:13:42.210
So this is alpha decay.

0:13:42.210,0:13:46.100
So this right here is[br]an alpha particle.

0:13:46.100,0:13:48.400
And this is an example[br]of alpha decay.

0:13:48.400,0:13:51.110
Now you're probably saying, hey[br]Sal, wait, something weird

0:13:51.110,0:13:51.850
is happening here.

0:13:51.850,0:13:56.630
Because if I just go from 92[br]protons to 90 protons, I still

0:13:56.630,0:13:59.430
have my 92 electrons out here.

0:13:59.430,0:14:02.750
So wouldn't I now have[br]a minus 2 charge?

0:14:02.750,0:14:08.270
And even better, this helium I'm[br]releasing, it doesn't have

0:14:08.270,0:14:09.090
any electrons with it.

0:14:09.090,0:14:10.390
It's just a helium nucleus.

0:14:10.390,0:14:12.700
So doesn't that have[br]a plus 2 charge?

0:14:12.700,0:14:15.180
And if you said that, you would[br]be absolutely correct.

0:14:15.180,0:14:19.510
But the reality is that right[br]when this decay happens, this

0:14:19.510,0:14:22.290
thorium, it has no reason[br]to hold on to those two

0:14:22.290,0:14:25.050
electrons, so those two[br]electrons disappear and

0:14:25.050,0:14:26.840
thorium becomes neutral again.

0:14:26.840,0:14:30.480
And this helium, likewise,[br]it is very quick.

0:14:30.480,0:14:33.040
It really wants two electrons[br]to get stable, so it's very

0:14:33.040,0:14:36.880
quick to grab two electrons out[br]of wherever it's bumping

0:14:36.880,0:14:38.460
into, and so that[br]becomes stable.

0:14:38.460,0:14:40.305
So you could write[br]it either way.

0:14:40.305,0:14:42.250
Now let's do another one.

0:14:42.250,0:14:43.500
So here I have iodine.

0:14:43.500,0:14:45.820


0:14:45.820,0:14:46.670
Let's see what's happening.

0:14:46.670,0:14:51.020
My mass is not changing.

0:14:51.020,0:14:53.790
So I must just have protons[br]turning into neutrons or

0:14:53.790,0:14:55.560
neutrons turning into protons.

0:14:55.560,0:14:58.810
And I see here that I[br]have 53 protons, and

0:14:58.810,0:15:00.800
now I have 54 protons.

0:15:00.800,0:15:04.060
So a neutron must have[br]turned into a proton.

0:15:04.060,0:15:06.830
A neutron must have[br]gone to a proton.

0:15:06.830,0:15:09.160
And the way that a neutron[br]goes to a proton is by

0:15:09.160,0:15:11.620
releasing an electron.

0:15:11.620,0:15:13.360
And we see that in this[br]reaction right here.

0:15:13.360,0:15:16.880
An electron has been released.

0:15:16.880,0:15:19.130
And so this is beta decay.

0:15:19.130,0:15:20.380
This is a beta particle.

0:15:20.380,0:15:25.580


0:15:25.580,0:15:26.750
And that same logic holds.

0:15:26.750,0:15:32.780
You're like, hey wait, I just[br]went from 53 to 54 protons.

0:15:32.780,0:15:34.440
Now that I have this extra[br]proton, won't I have a

0:15:34.440,0:15:35.750
positive charge here?

0:15:35.750,0:15:36.480
Well you would.

0:15:36.480,0:15:40.810
But very quickly this might--[br]probably won't get these exact

0:15:40.810,0:15:42.740
electrons, there's so many[br]electrons running around-- but

0:15:42.740,0:15:45.950
it'll grab some electrons from[br]some place to get stable, and

0:15:45.950,0:15:47.080
then it'll be stable again.

0:15:47.080,0:15:48.890
But you're completely right in[br]thinking, hey, wouldn't it be

0:15:48.890,0:15:51.690
an ion for some small[br]amount of time?

0:15:51.690,0:15:52.900
Now let's do one more.

0:15:52.900,0:15:57.210
So we have to 222-radon-- it[br]has atomic number of 86--

0:15:57.210,0:16:01.720
going to 218-polonium, with[br]atomic number of 84.

0:16:01.720,0:16:03.540
And this actually is an[br]interesting aside.

0:16:03.540,0:16:08.380
Polonium is named after Poland,[br]because Marie Curie,

0:16:08.380,0:16:11.220
she-- At the time Poland, this[br]was at the turn of the last

0:16:11.220,0:16:15.120
century, around the end of the[br]1800's, Poland didn't exist as

0:16:15.120,0:16:15.910
a separate country.

0:16:15.910,0:16:19.540
It was split between Prussia,[br]Russia, and Austria.

0:16:19.540,0:16:21.590
And they really wanted let[br]people know that, hey, you

0:16:21.590,0:16:24.000
know, we think we're[br]one people.

0:16:24.000,0:16:27.170
So they discovered that when,[br]you know, radon decayed it

0:16:27.170,0:16:27.730
formed this element.

0:16:27.730,0:16:31.430
And they named it after their[br]motherland, after Poland.

0:16:31.430,0:16:33.880
It's the privileges of[br]discovering new elements.

0:16:33.880,0:16:35.090
But anyway, back[br]to the problem.

0:16:35.090,0:16:35.930
So what happened?

0:16:35.930,0:16:39.210
Our atomic mass went[br]down by four.

0:16:39.210,0:16:41.430
Our atomic number went[br]down by two.

0:16:41.430,0:16:44.580
Once again, we must have[br]released a helium particle.

0:16:44.580,0:16:47.070
A helium nucleus, something[br]that has an atomic mass of

0:16:47.070,0:16:51.160
four, and an atomic[br]number of two.

0:16:51.160,0:16:52.100
And so there we are.

0:16:52.100,0:16:55.950
So this is alpha decay.

0:16:55.950,0:16:57.810
We could write this as[br]a helium nucleus.

0:16:57.810,0:16:59.145
So it has no electrons.

0:16:59.145,0:17:00.820
We could even say immediately[br]that this would have a

0:17:00.820,0:17:02.990
negative charge, but[br]then it loses