0:02 what are isotopes isotope is a word that
0:05 gets thrown around in chemistry a lot so
0:08 like what are they really quickly
0:10 Isotopes are different versions of an
0:12 element or different versions of a
0:15 certain kind of atom this can be a
0:17 tricky concept though and a lot of
0:19 people get confused by Isotopes so I
0:22 want to describe them by starting out
0:26 with an analogy to cars okay I want to
0:29 talk to you about the madeup car called
0:30 The Lamona
0:34 the epitome of luxury and it's known for
0:36 its very distinctive styling as you'll
0:39 see the lemona looks like a lemon now
0:43 the Lamona comes in three different
0:46 models there's the lemona G the Lamona
0:49 GX and the Lamona
0:51 gxl they're all different colors as you
0:54 can see but each of these models also
0:58 has unique features one has a radio and
1:00 leather seats the GX here has chrome
1:04 wheels and a CD player it's blue the red
1:06 gxl has massaging seats Platinum spinner
1:08 wheels and everything but here's the
1:12 point they are all Lonas they're all
1:14 Lonas because they all have this
1:16 distinctive styling they look like a
1:18 lemon and that's what makes a car a
1:21 lemona okay so it doesn't matter what
1:23 color it is and it doesn't matter the
1:25 various options that you get in these
1:29 models the G the GX or the gxl what matters
1:30 matters
1:33 is that they all have this particular
1:36 shape that's what makes a Lona a Lon so
1:39 we have these three different
1:42 models I want to use this analogy now to
1:45 talk about the same thing but with atoms
1:48 I want to now introduce you to three
1:50 models of carbon just the way they're
1:53 three models of Lon okay here are the
1:55 drawings of each one of them and what
1:56 we're particularly concerned about is
1:59 the nucleus I'm using these red dots to
2:02 symbolize protons and I'm using the blue
2:06 dots to symbolize neutrons the swirly
2:08 circles are supposed to represent
2:09 electrons that are buzzing around the
2:10 nucleus but we don't really want to
2:13 worry about that too much right now
2:17 anyway these three models of carbon are
2:22 carbon 12 carbon 13 and carbon 14 let's
2:25 look at the options in them like we did
2:27 with Alona let's look at how each one of
2:29 these different types of carbon differs
2:32 okay so if we count the number of
2:33 protons in carbon 12 we'll see that it
2:36 have six protons and if I count all the
2:39 blue spots here I have six neutrons okay
2:45 carbon 13 1 2 3 4 5 six red spots six
2:48 protons in this one I have seven
2:51 neutrons and in carbon 14 down here I
2:53 have six
2:56 protons and I have eight
2:58 neutrons so what do we have in common
3:00 here all the different models of the
3:02 Lona even though there are things that
3:04 they differed about all have the same
3:08 distinctive lemonlike shape so for
3:11 carbon what they all have in common is
3:13 they have six
3:16 protons six protons in the nucleus and
3:19 that's what makes a carbon atom a carbon
3:22 atom okay so it turns out that it
3:24 doesn't matter how many neutrons it has
3:26 six neutrons seven neutrons eight
3:28 neutrons no big deal it's just like
3:30 painting Lona different colors or adding
3:33 a radio or a CD player the neutrons it
3:35 doesn't matter it doesn't change the
3:38 fact that each one of these are a
3:42 carbon that's because carbon is defined
3:45 by the fact that it has six protons in
3:46 its nucleus if you look it up on the
3:48 periodic table you'll see something that
3:49 looks like this and the number up here
3:52 is the atomic number six which means
3:55 that if an atom has six protons it's
4:00 carbon okay so that's what these all are
4:02 they all isotopes of carbon they're
4:04 different versions of carbon or
4:06 different models of carbon with the same
4:08 number of protons and different number of
4:08 of
4:12 neutrons so look at how I wrote this got
4:14 carbon 12 carbon 13 carbon 14 up here I
4:15 want to take a minute and talk about the
4:18 numbers so the number of protons in the
4:23 nucleus we call that the atomic
4:25 number you may already know that and
4:28 then carbon 12 this 12 that I've written
4:31 here refers to to a different number and
4:35 we call that the mass number the mass
4:38 number as you'll see is the number of
4:41 protons plus the number of neutrons so
4:43 this is carbon 12 6 + 7 protons and
4:47 neutrons is 13 here 6 Plus 8 is carbon
4:49 14 here so that's how we distinguish
4:51 between these different isotopes
4:54 different types of carbon there's
4:56 another way that we sometimes indicate
4:58 these different isotopes of an atom
5:00 instead of doing 12 and 1 or 14 and
5:02 that's by using something called isotope
5:05 notation let me show you how we do that
5:07 the way we write carbon 12 or 13 or 14
5:09 and isotope notation is we start out
5:11 with a chemical symbol if you don't
5:12 already know that you can find it on the
5:15 periodic table so here it is it's a big
5:16 upper case C
5:18 C
5:22 so I start with my C for carbon and then
5:25 on the lower corner here I write the
5:27 atomic number so that's going to be six
5:30 and then up top I write the mass number
5:33 which is 12 so this is carbon 12 written
5:37 in isotope notation carbon 13 is going
5:39 to be 6 again because all carbon has six
5:42 protons in its nucleus but then the 13
5:46 up here and finally carbon 14 written in
5:48 isotope notation is
5:51 c614 so that's how we can write all
5:54 these isotopes of carbon in isotope
5:55 notation and of course you can also
5:57 write it as just the element name with a
6:00 dash and then the number so carbon isn't
6:02 the only type of element that has
6:05 multiple Isotopes in fact just like cars
6:08 almost every form of element comes in multiple
6:09 multiple
6:12 Isotopes here are the calcium Isotopes
6:14 for example if you look up on the
6:16 periodic table you'll see that calcium
6:18 has an atomic number of 20 which means
6:20 that any atom that has 20 protons in its
6:23 nucleus is calcium but just like with
6:25 carbon you can vary the number of
6:27 neutrons that are in the nucleus you get
6:28 all these different isotopes but you
6:31 still have calcium calcium we got 40 42
6:35 43 44 46 48 all of them have 20 protons
6:37 in the nucleus but they have varying
6:40 numbers of neutrons just like we did
6:42 with carbon we can write all of these
6:44 calcium Isotopes in isotope notation
6:47 where we have the mass number here up at
6:49 the top and the atomic number down at
6:51 the bottom you'll see they all have the
6:54 same atomic number of 20 but different
6:57 Mass numbers the sum of protons and
6:59 neutrons the same is true for iron just
7:04 to give you another example iron has 26
7:06 protons in its nucleus an atomic number
7:09 of 26 and there are four known isotopes
7:13 of iron all of which have 26 protons in
7:14 the nucleus but they all have varying
7:16 numbers of neutrons you add these
7:18 together to get the mass number and then
7:20 you can write it in isotope notation
7:22 with a mass number up here and the
7:24 atomic number down here so just to
7:27 review what we've talked about atoms
7:29 come in different versions known as
7:31 Isotopes these are like the different
7:33 versions of a car or something the
7:35 number of neutrons change but just as
7:37 long as you have the same number of
7:39 protons you still have the same type of
7:42 atom the same type of element you can
7:45 take uh an atom and write it in isotope
7:49 notation where you put the atomic number
7:51 on the bottom and the mass number up
7:54 here so that is uh that's what Isotopes are
