0:03 let's take a closer look at atoms atoms
0:05 are the building blocks that make up
0:09 everything all stuff everywhere here
0:10 I've got some
0:15 drawings this is table salt a solid
0:19 here's water a liquid and finally oxygen
0:22 gas and what we're looking at here is
0:24 what we'd see if we could take these
0:28 three things and zoom in zillions and
0:30 zillions and zillions of times
0:33 and if we could look at these closely
0:36 enough we'd be able to see the atoms
0:39 these little building blocks that make
0:42 everything up now atoms aren't really
0:45 little colored circles but it's a good
0:46 way to think about them and it's the way
0:47 we'll usually draw them when we're
0:50 learning about this stuff atoms are
0:53 super tiny they are so tiny it can be
0:55 really hard to wrap your head around how
0:56 tiny they are here is something that
1:00 might help you think about this take a
1:04 piece of paper look at how wide it is
1:08 here all right this is so incredibly
1:13 thin now atoms are so small that it
1:18 would take one million atoms lined up
1:22 next to each other in a row to be as
1:27 thick as this tiny width of paper that's
1:30 how small atoms are now what I want to
1:33 do now is look even closer at an at
1:36 let's take one of these atoms here and
1:38 zoom in even more so we can see what's
1:42 inside of it here's a magnified view of
1:44 one atom it's not a perfect
1:46 representation of exactly what an atom
1:48 would look like but it's close enough
1:50 for right now and check this out the
1:54 atom itself is made up of even smaller
1:57 things right so that we said adoms are
1:59 like the building block for all of stuff
2:02 but then if you look at an atom it has
2:04 even smaller building blocks that make
2:08 it up so in the center of the atom is
2:09 something called the
2:12 nucleus and the nucleus is made up of
2:16 two tiny particles there are protons
2:18 which I've drawn as red circles here and
2:21 then they're neutrons which I've drawn
2:22 as blue circles nucleus is here in the
2:25 middle of the atom and then on the
2:28 outside of the atom there are these uh
2:31 little black circles that I'm using to
2:33 uh to represent
2:35 electrons the electrons you'll see are
2:38 connected to these sort of oval paths
2:40 and I've drawn these in to show that the
2:44 electrons are constantly moving they're
2:46 flying around the outside of the atom at
2:49 an incredibly high speed whereas the
2:53 nucleus stays solid here right in the
2:57 middle of the atom now electric charge
2:58 is very important when we're talking
3:01 about atoms for number number of reasons
3:04 protons have a positive charge a proton
3:07 has a charge of 1 plus electrons on the
3:10 other hand have a negative charge one
3:13 electron has a charge of one minus now
3:15 neutrons they don't have an electric
3:18 charge at all they have a charge of zero
3:20 and neutral is a word that we use to
3:21 refer to something that doesn't have a
3:25 charge so neutrons sounds a lot like
3:28 neutral now positive and negative
3:31 charges attract remember that opposite
3:34 charge is attract and that has important
3:36 consequences for how this atom works we
3:38 said that these electrons are flying
3:40 around the outside of the atom they're
3:42 moving really fast so why don't they
3:45 just fly out into space well the reason
3:47 why is because the negatively charged
3:49 electrons are attracted to the
3:52 positively charged protons so the
3:54 protons kind of pull the electrons in
3:56 they keep them from just flying
4:00 away but the electrons are moving around
4:02 so fast that they're not able to
4:05 actually pull in here and actually touch
4:08 the protons so that's why they keep
4:09 staying on the outside and don't just
4:12 crash in here and all touch the
4:14 protons now sometimes people ask well
4:16 neutrons neutrons don't have a charge
4:19 why are they important at all well it
4:22 seems that neutrons help keep all of the
4:25 particles in the nucleus strongly
4:27 connected to each other now electrical
4:29 charge is important something else
4:31 that's important animportant with atoms
4:33 is what their mass is how much they
4:36 weigh so in order to figure that out we
4:38 have to look at the mass of the various
4:41 things that make up the atom now a
4:44 proton and a neutron are very very
4:48 similar in size and in mass and they
4:52 both weigh about this many grams look at
4:54 what a tiny number this is right there's
4:56 a decimal place all the way over here
4:58 this is a number that it's best to
5:02 represent in scientific notation instead
5:06 but however you write this it's a really
5:09 tiny unwieldy number so scientists came
5:11 up with another way to uh to measure the
5:13 mass of a proton or Neutron and that's
5:17 using a unit called the AMU the atomic
5:20 mass unit and they said okay one proton
5:22 or one Neutron weighs about 1 AMU that's
5:25 a lot easier to use than this
5:27 measurement here so Proton or Neutron
5:30 weighs about 1 Amu an electron on the
5:33 other hand is much much much smaller
5:43 0549 AMU so a tiny fraction of how much
5:46 a Proton or Neutron weighs for this
5:48 reason when we're talking about the mass
5:51 of atoms which we'll talk about later on
5:53 we usually add up the protons and
5:56 neutrons to find out how many amus um
5:58 the atom weighs and then we usually
6:00 don't even worry about the El r at all
6:02 because they're just they're so tiny
6:04 they don't really have much of an
6:08 influence on how much an atom weighs
6:10 it's like when you get on a scale to
6:12 weigh yourself you don't worry about the
6:14 ring you're wearing or whether you're
6:15 wearing a necklace or something because
6:17 those things are just so tiny they weigh
6:20 so little compared to how much you weigh
6:21 that it doesn't really influence your
6:26 weight so protons and neutrons 1 AMU and
6:29 electrons a tiny fraction of that now I
6:31 said the atom the way it's drawn here
6:33 isn't a perfect representation of what
6:34 atoms would actually look like we'll
6:36 talk more about that later but there are
6:37 two things that I want to bring up for
6:40 right now the first is the electrons and
6:42 how they move this drawing might make
6:44 you think that the electrons are
6:47 spinning around in nice circles on the
6:49 outside of the atom that's actually not
6:51 what happens they're buzzing around much
6:54 more randomly kind of like hyperactive
6:56 flies all over the place we'll talk more
6:59 about that later the second thing has to
7:02 do with the size of the nucleus and how
7:04 far the electrons are from it If This
7:07 Were a real atom blown up many many
7:09 times and the nucleus were the size of a
7:13 grape the electrons out here would be
7:17 almost a mile away have this grap siiz
7:20 nucleus and a mile away would be the
7:23 electron spinning on the outside so that
7:27 means that most of an atom is actually
7:30 empty space anyway
7:32 now that we've talked about what an atom
7:33 looks like and the particles that make
7:36 it up we can go and discuss some of the
7:37 characteristics that we can use to
7:40 describe atoms these are things like
7:43 like atomic number mass number and net charge
