00:00:01
all right guys let's get into some super
00:00:03
crazy stuff here we're going to uh start
00:00:05
broadcast 5.2 um where we're going to be
00:00:07
talking um about energy levels um and
00:00:10
what that means is that if we look at a
00:00:13
boore model of the atom okay so if you
00:00:16
recall um back when we did our little
00:00:19
bit on development of atomic theory that
00:00:21
the Board model um was in general
00:00:24
called the planetary model OKAY was
00:00:28
called the planetary model because we've
00:00:30
got these orbits okay in which electrons
00:00:33
okay so this electron are circling the
00:00:36
nucleus kind of like planets are
00:00:38
circling the Sun and they're in these
00:00:39
very specific orbits so there's an orbit
00:00:42
here and one here and one here and here
00:00:44
and then so on and so forth and bore
00:00:46
labels each of these Nal 1 2 3 4 5 six
00:00:50
7even okay on all the way out um and so
00:00:55
nucleus in the middle that's where the
00:00:56
protons and neutrons are electrons are
00:00:58
then in these orbits okay so that's the
00:01:01
essential bore model what we're going to
00:01:03
see here is what's important is these
00:01:04
energy levels and what happens with the
00:01:07
interaction um between things with these
00:01:09
energy levels okay so let's jump over to
00:01:13
our next slide here and see something
00:01:15
that looks really different than
00:01:16
anything we've seen before um this all
00:01:18
has to do with something called
00:01:20
spectroscopy U and what spectroscopy
00:01:22
means is and it's pretty easy but
00:01:24
spectroscopy has to do with Spectrum
00:01:27
okay you guys have all seen um light it
00:01:29
goes through a prism and it splits up
00:01:31
and sort of forms a rainbow um well you
00:01:33
can do that too with atoms um with
00:01:36
specific elements um and so I'm going to
00:01:38
show you a short little video clip here
00:01:40
um that represents this right here which
00:01:42
is a hydrogen gas in a tube and
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basically if you apply a lot of energy
00:01:46
to it that hydrogen gas is going to glow
00:01:49
and it's going to emit light if you then
00:01:51
pass that light through these slits you
00:01:53
can separated out into these different
00:01:56
bands okay so we're going to take a
00:01:58
quick pause and watch that video clip
00:01:59
and then we'll come come back here to
00:02:01
okay so real quick this is the hydrogen
00:02:03
Spectrum notice it's making a loud
00:02:05
buzzing that's the uh electricity going
00:02:07
in there we're going to put a
00:02:08
spectroscope up to this and if you look
00:02:10
real close you can see some of these
00:02:11
sharp little lines that we're talking
00:02:13
about so here comes the spectroscope no
00:02:15
it's kind of hard to see because I got a
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camera over you see those sharp lines
00:02:18
that's what we're looking for those are
00:02:20
the
00:02:22
Spectrum this
00:02:26
part okay so what what we saw there was
00:02:30
that and you couldn't really see it in
00:02:31
the video because again I'm trying to
00:02:32
look through a spectroscope with a
00:02:34
camera which doesn't work terribly well
00:02:36
um but what happens there is that you
00:02:38
start to see these very distinct lines
00:02:40
of very distinct colors um this is
00:02:42
what's called an emission spectrum okay
00:02:45
um there's different kinds of spectrum
00:02:46
you can do absorption uh Spectrum where
00:02:48
basically this is reversed but this is
00:02:50
called an emission spectrum and this is
00:02:51
if you look down here um this is the
00:02:55
wavelength okay what we're measuring in
00:02:58
each P place is the wavelength length of
00:03:00
that energy we're going to talk a little
00:03:02
bit more about wavelength here in a
00:03:03
second okay but the idea is that every
00:03:07
element okay has a specific emission
00:03:09
Spectra that if you excite it if you
00:03:11
heat it up then it's going to give off
00:03:13
these certain ways of light now the
00:03:15
whole reason for this and bore is the
00:03:17
guy that discovers the reason for this
00:03:19
because they' known about emission
00:03:20
spectrum for a while what they didn't
00:03:22
really know is why it was happening in a
00:03:24
specific way and why certain elements
00:03:26
gave off these certain patterns so if we
00:03:28
look right here here and what is called
00:03:31
the Balmer
00:03:32
series okay you see that there are four
00:03:35
lines here 410 434 486 656 nanometers
00:03:40
those lines correspond to these colors
00:03:45
okay these bands of color that we get
00:03:47
when we excite the hydrogen now so the
00:03:49
question is then what is going on there
00:03:52
um in those bands well here's what
00:03:54
happens so in the boore model there's
00:03:56
these energy levels right 1 two 3 4 five
00:04:00
six so on and so forth what happens is
00:04:03
that in a normal hydrogen atom okay the
00:04:06
electron is down here in n equals 1 okay
00:04:10
in under normal circumstances if we put
00:04:12
energy in it jumps up out of that level
00:04:15
into higher levels it becomes what we
00:04:17
call an excited electron okay and
00:04:21
excited just means that it's not in the
00:04:23
normal energy level okay that it's
00:04:25
higher up than its ground state so any
00:04:28
of these for hydrogen would the excited
00:04:30
levels if an electron was down here at
00:04:32
the bottom um we would call that the
00:04:36
ground state okay so that's its normal
00:04:38
position and if we put energy in it gets
00:04:40
excited now once it gets excited they're
00:04:43
going to start to fall back down and
00:04:44
when they fall back down they emit
00:04:46
radiation okay electromagnetic radiation
00:04:49
and if they emit it in this range okay
00:04:52
right here this is what's called visible
00:04:54
light and that's the part that we can
00:04:55
actually see you can see that there are
00:04:57
parts of it that are emitted outside of
00:05:00
visible light okay so we got infrared
00:05:02
over here and UltraViolet over here so
00:05:04
we can detect those as well but the part
00:05:06
that we're really interested in is the
00:05:08
spectroscopy that gives us this very
00:05:10
specific Spectrum okay um every element
00:05:15
um essentially and a lot of compounds as
00:05:17
well have very distinct spectrum that
00:05:20
they give if you ever wondered like
00:05:21
where astronomers like you know they say
00:05:24
hey we found um a planet and its
00:05:26
atmosphere we believe is mostly methane
00:05:28
or something like that and you're like
00:05:30
well how the heck do they know that the
00:05:31
atmosphere is methane I mean they they
00:05:34
not like they've been to that planet and
00:05:35
sampled it they know because of
00:05:37
spectroscopy they can look at it with
00:05:38
specific instruments they can see these
00:05:41
bands and every element and most
00:05:44
compounds um have a very specific band
00:05:47
kind of like a
00:05:48
fingerprint um for an element or a
00:05:51
compound okay so
00:05:54
specific okay to an element okay or a
00:05:58
compound for that matter
00:06:00
um and it's like a
00:06:02
fingerprint okay so it's sort of a
00:06:05
unique identifier and indeed this is one
00:06:07
of the ways that they like if you do
00:06:08
blood work or something like that that
00:06:10
they're going to measure say um how much
00:06:13
maybe potassium is in your blood is
00:06:15
they're going to take your blood sample
00:06:16
and they're going to run it through a
00:06:17
machine but what the machine is actually
00:06:18
doing is getting one of these emission
00:06:21
spectrum okay and they can then identify
00:06:24
the bands and say hey that's potassium
00:06:25
and we've got this much of it okay so
00:06:28
what is this mean to us well first off
00:06:31
um B's model worked really well for the
00:06:34
hydrogen atom um but the problem was
00:06:37
they found out that it didn't work for
00:06:38
anything else okay and the reason for
00:06:41
that is that everything else there's
00:06:42
more than one electron and so things
00:06:44
started to get really ridiculously
00:06:47
complicated when you added in extra
00:06:49
electrons so this over here to the side
00:06:52
this is the modern model of the atom
00:06:54
okay and what's going on here is we've
00:06:56
got a cloud you see this sort of
00:06:57
fuzziness nucleus is in the middle
00:06:59
little tiny spot in the middle remember
00:07:00
Rutherford found out that nucleus was in
00:07:02
the middle and that it took up hardly
00:07:04
any space at all and then this fuzzy
00:07:06
area on the outside that's the electron
00:07:07
cloud now we're going to talk a lot more
00:07:09
about what where the electrons actually
00:07:10
are there in a little bit um but what is
00:07:13
so what does that have to do with this
00:07:15
Bard model that we've been talking about
00:07:16
well let's see if we can relate this to
00:07:18
energy in the electrons okay so we need
00:07:20
to learn a couple of quick terms um and
00:07:23
these terms that are really important to
00:07:24
us here are wavelength that was some
00:07:27
awesome circling and frequency okay and
00:07:30
this is what wavelength is wavelength is
00:07:32
just what it sounds like it's the length
00:07:34
of a wave okay light and infrared and
00:07:37
gamma rays and all that those are part
00:07:38
of the electromagnetic spectrum okay
00:07:41
which is radiation and radiation has is
00:07:44
a wave function we'll talk later that
00:07:46
it's if you take other science class
00:07:47
it's not technically just a wave but
00:07:49
anyway it's a wave function and so the
00:07:51
length of the wave from one Peak to the
00:07:53
next Peak is a wavelength or from one
00:07:55
midpoint to another midpoint is a
00:07:57
wavelength basically from any one point
00:07:59
to the exact same point on the next wave
00:08:02
that's a wavelength we measure it in
00:08:03
meters or usually considering how small
00:08:05
they are something like nanometers if
00:08:07
we're talking about um for if for
00:08:10
instance if we're talking about uh light
00:08:12
it's going to be in nanometers and
00:08:13
that's what those measurements were back
00:08:14
on the hydrogen Spectrum um the second
00:08:16
definition is something called frequency
00:08:18
frequency is basically the inverse
00:08:20
function of wavelength and frequency if
00:08:23
you see here on this GIF um frequency is
00:08:25
how many wavelengths pass a given point
00:08:27
in a second okay
00:08:29
um and it's measured in hertz which is
00:08:32
basically one over second or cycles per
00:08:35
second okay um Hertz is
00:08:38
HZ okay and if we had actually had to
00:08:41
write out the unit it would be one over
00:08:43
seconds or sometimes you'll see it
00:08:45
written as this they all mean the same
00:08:47
thing basically just means how many
00:08:48
waves pass by in a second and what you
00:08:50
can see here in this GIF is that uh the
00:08:52
Herz is going up as the waves get more
00:08:55
compacted as they get pressed together a
00:08:56
little bit more um the the frequency is
00:08:59
going to go up and as they're spread
00:09:01
apart more so like right now they're
00:09:03
getting really crunched together then
00:09:04
the frequency is higher so it's about
00:09:06
five Hertz there as they're really far
00:09:08
apart and the Herz is low that means
00:09:10
that you've got a really big wavelength
00:09:12
so they're inversely related okay and
00:09:14
that's going to lead us to a couple of
00:09:16
math formulas now we're not going to
00:09:18
work a whole bunch of these we'll work a
00:09:19
couple in class just because I want you
00:09:20
to be familiar with them because we may
00:09:22
see a couple um but we won't stress too
00:09:24
much about it just make sure that you
00:09:26
understand what the terms are and how to
00:09:28
plug stuff in they're just algebra
00:09:29
equations so here's our first equation
00:09:32
um it's called the Lambda V equation so
00:09:34
C equals Lambda V this weird looking
00:09:37
letter here um is called a Lambda okay
00:09:40
um and if you're wondering how that's
00:09:42
spelled okay that is it's a Greek letter
00:09:45
and it's spelled oh I messed it up l a m
00:09:49
BDA Lambda okay and so C equals Lambda v
00:09:53
c is the speed of light if you remember
00:09:55
um Einstein's equation that we sort of
00:09:57
see written up all the time the e = mc^2
00:10:01
it's the same c as in that equation Okay
00:10:04
C is the speed of light it's uh 3.0 *
00:10:06
108 meters per second which is really
00:10:09
fast doesn't I mean it's kind of a big
00:10:11
number but it doesn't sound like much
00:10:12
but that is pretty fast it's basically
00:10:14
as fast as anything we know can go
00:10:16
unless that neutrino experiment that
00:10:18
just happened is true um Lambda is the
00:10:19
wavelength it's usually in meters um if
00:10:22
it's in anything but meters that you'll
00:10:24
need to change it and the way it's
00:10:26
usually going to be written for us is
00:10:27
nanometers um so we sort of need an
00:10:30
equality there and the way that works is
00:10:31
that um 1 meter equal 10 9th nanometers
00:10:37
or basically a billion nanometers okay
00:10:41
and V is in frequency we already said
00:10:42
that that's in hertz or in one over
00:10:45
seconds okay so we're going to work a
00:10:47
real quick problem here just so we can
00:10:48
see how this works and we'll work one
00:10:49
more equation after this probably so
00:10:52
what is a frequency of red light with a
00:10:53
wavelength of 656 NM so as soon as you
00:10:57
see that um you should immediately
00:10:59
convert your nanometers into meters now
00:11:03
there's a couple of ways that you could
00:11:04
do that you could use the staircase and
00:11:06
move it nine spaces which might actually
00:11:08
be easier or you can do a real quick
00:11:11
conversion factor just like this okay if
00:11:15
we calculate this out whoops I totally
00:11:17
wrote that wrong didn't I 56 we're going
00:11:19
to get
00:11:21
6.56 * 10
00:11:23
the7th m okay now that is my Lambda
00:11:29
value okay
00:11:32
Lambda so our equation then remember is
00:11:35
C equals Lambda
00:11:38
V okay I know Lambda C is a constant
00:11:41
it's always 3.0 * 108 so we're just
00:11:45
going to plug this stuff
00:11:46
in time 10 and that's to the e8th not
00:11:49
negative e meters per second
00:11:52
equals
00:11:55
6.5 that is some bad handwriting Arnold
00:11:59
okay
00:12:02
6.56 *
00:12:04
107 M that's what we just found up here
00:12:07
okay that goes right in there and that's
00:12:09
times V and V of course is what I'm
00:12:12
looking for okay so we're going to punch
00:12:15
that into the calculator now
00:12:16
algebraically what do we need to do um
00:12:17
if I want V by itself which is what I'm
00:12:19
solving for I'm going to divide both
00:12:21
sides by the
00:12:25
wavelength okay so divide both sides by
00:12:28
that
00:12:30
and of course you don't actually have to
00:12:31
necessarily write out this entire step
00:12:34
of algebra if you're doing this but if
00:12:36
you're uncomfortable with it that'll
00:12:37
work so that cancels out this side punch
00:12:40
this number into our calculator and
00:12:42
we're going to get
00:12:44
4.54 okay three sigfigs time 10 14th
00:12:49
Hertz now what this means really small
00:12:52
wave length Okay time 10 the -7th M okay
00:12:57
means really big frequency they're
00:12:58
inverse ly proportional now why was that
00:13:01
important what did that have to do with
00:13:02
the Bor mod it has to do with this
00:13:03
because once we know
00:13:05
frequency we can then calculate the
00:13:07
energy and why do we care about energy
00:13:09
because if I go back several slides okay
00:13:14
the energy is what's given off here okay
00:13:17
and the energy then leads to these
00:13:19
frequencies so for each of these
00:13:20
individual frequencies we could or um
00:13:23
wavelengths we could calculate the
00:13:25
frequency and then turn those into
00:13:27
energy using these two equations and
00:13:29
that's exactly what scientists do okay
00:13:32
so real quick let me work one of these
00:13:33
equations equation itself pretty easy
00:13:35
energy is equal to H time v um e is
00:13:38
energy in Jewels V is the frequency that
00:13:40
we had in the last equation and H is a
00:13:43
constant it's called planks constant and
00:13:45
it's this is its number super small
00:13:48
number that's a smaller number than
00:13:50
aag's number is Big 6.62 6 time 10 34th
00:13:54
really tiny number we did one of those
00:13:57
back in scientific notation time
00:13:59
okay so real quick let's work one of
00:14:01
these problems um it won't take us too
00:14:02
long so let's just crank one out so E
00:14:05
equals
00:14:06
HV okay I guess we should read the
00:14:08
problem first given a frequency of 1.60
00:14:11
* 10 15th Hertz what is the energy of
00:14:13
this particle so I'm looking for energy
00:14:15
energy is e okay I'm given frequency
00:14:18
frequency is V and H is a constant okay
00:14:23
remember that's from the last slide so H
00:14:26
is equal to
00:14:27
6.62 6 * 10
00:14:32
34th okay you might not have noticed the
00:14:35
ules the units on it the ules the units
00:14:37
it's jewles times seconds and the reason
00:14:39
for that is that remember Hertz is one
00:14:42
over seconds so when we multiply This
00:14:44
Together the seconds cancel and we're
00:14:45
left with jewels and that's exactly what
00:14:47
we want to happen so this one's even
00:14:48
more straightforward than the last one
00:14:50
because I'm just going to plug it in and
00:14:51
then punch stuff into my calculator so
00:14:53
6.
00:14:55
626 * 10 to the negative sorry about
00:14:58
these negative signs I know I'm B- 34
00:15:01
Jew time seconds okay and that's
00:15:04
multiplied by our frequency that's given
00:15:07
to us in the problem
00:15:09
1.60 * 10 15 and you don't even have to
00:15:12
do algebra for this problem okay
00:15:15
remember that Hertz is one over second
00:15:17
so that's going to mean that seconds are
00:15:19
going to cancel and we're just going to
00:15:21
be left with
00:15:22
jewels you just punch that into the
00:15:24
calculator there's no real algebra that
00:15:25
needs to and you just got to do the math
00:15:27
punch it in the calculator so 1.06 * 10
00:15:31
to the
00:15:32
Nega
00:15:34
negative
00:15:36
18th Jewels okay let me clean that up
00:15:39
just a little bit because I know that's
00:15:40
a little hard to see okay so negative
00:15:43
18th Jewels that's a pretty small number
00:15:46
um and it should be I mean we're talking
00:15:47
about one little particle okay one
00:15:50
electron moving one energy level in one
00:15:52
atom could to be a pretty small amount
00:15:54
obviously if that happens in a lot of
00:15:55
them then that becomes a much bigger
00:15:57
amount okay we're probably not going to
00:15:59
do a a a massive ton of these
00:16:01
calculations but we'll work through four
00:16:02
or five in class just to make sure we
00:16:04
know how to do this and then we'll move
00:16:05
on in the next section to the real
00:16:06
important stuff which is electron
00:16:09
configurations thanks guys
