Bohr Atomic model - Structure of Atom Video Lecture - Class 11

welcome back my young think allergist
today's quick chemistry fact is about
the atomic model of the atom
specifically the modern atomic model of
the atom modern atomic model and the
individual who played a major role in
the modern atomic model of the atom is
Niels Bohr very famous quantum physicist
he basically said this now if you look
at Rutherford's atomic model which as we
all know kind of looked like this right
here which was a solar system like model
and he said okay if this is going to
work atoms have to have defined orbital
shells the electrons have to be in these
defined orbital shells in order for this
to work he also said that these orbital
shells themselves actually have defined
shapes and the math involved defined
this everybody if you've ever heard of
quantum mechanics it's very tough math
that's involved in actually
determination of a lot of this stuff now
more importantly these shells and these
shapes are quantized one
now all that means is to be quantized is
to limit some thing to a set number of
possible values so the set number of
values is actually the shells and you'll
find out that you could go to an
infinite amount of shells on an atom and
that electron in that outermost shell
won't even play a part in actually being
on the nucleus or near the nucleus of
that atom so we actually have to
quantize the actual physical amount of
shells for this to work for even the
largest atoms on the periodic table and
let's show this now if we look at helium
let's look at helium that's a that's a
good one to start with
helium has two protons helium also has
two electrons and lastly helium has let
me pick a nice color here well let's
pick yellow helium has two neutrons okay
as a fact you can get all this
information on the periodic table just
by looking at the atomic number of
helium and the mass number of helium so
I'm just going to kind of draw in little
circles here so there's one proton
here's another proton and let's put some
electrons in here sorry another electron
yeah oops let's go ahead and rate change
that color
let's put yellow four neutrons right
okay so a neutron and a neutron right so
two neutrons and two protons now corn
borer the electrons are in set positions
they're in set shells the question is
how many can I have in each of these
shells here that N equals one shell
right here and the N equals two an N
equals three
and actually N equals four n equals five
and equals six etc etc and actually
thing to note further out you go
I'll be closer that these shells get um
that just has to do with you know
keeping the outermost electrons intact
with the the nucleus of the atom and
holding stability across the board here
but relating back to determining exactly
how many electrons we have in our shells
now N equals one has only two electrons
that it's able to hold that's just
because it's so darn close to the
nucleus the nucleus will actually hold
those suckers and real tight they're not
going anywhere okay and actually these
electrons are in fact moving and defined
orbital shapes around the nucleus of
this atom okay let's go to another
example let's look at oh I don't know
let's just look at the next one let's
look at a lithium lithium okay that's
all not the number three on the periodic
table of elements
atomic number three and it has everybody
three protons if it's atomic number
three it has three protons it also has
three electrons and if you do some math
and subtract seven from three you
actually find out that it has four
protons I'll use yellow sari at protons
four neutrons
okay because it is atomic mass is seven
so four plus three is seven okay let me
draw some some protons so one two three
there's my protons let me put some
neutrons in one two three and four now
if you're wondering okay how did that
side where to put these I'm just putting
in random order here or just to
represent the nucleus okay so this is
four neutrons and three protons in
lithium okay everybody where do you
think these electrons are going to go in
N equals one well like I said you can
only hold two electrons in the lowest
energy level which is N equals one so
automatically you're going to have just
two electrons um and then where do you
suppose this next electrons going to go
that third one is in going N equals 2 N
equals 3 N equals 4 and it's 5 etc etc
well it'll just start to fill the next
orbital level so we're just going to
have an electron go into the next
orbital level and notice we only have
one electron in the N equals 2 energy
level guess what those electrons
actually have a name we call those in
chemistry valence electrons they have
their own name because they are
important hey do you all remember how we
get an eye on what happens to lithium if
this electron goes out well we're left
with more positive charge right here so
we actually get notice no longer lithium
but you get lithium plus and that's just
due to this valence electron here
jumping off the orbital shell okay so
notice the information does go full
circle let's do another example let's
look at I don't know let's look at the
noble gas
gasps and I'll talk about why we call it
a noble gas it wasn't developed by a
king or any any royalty let's look at
neon neon if you look at the periodic
table has ten protons also has 10
electrons from color sorry 10 electrons
and 10 neutrons yes I'm not going to
draw these all in
let's just go 10 neutrons and 10 protons
okay
so 10 neutrons 10 protons in the nucleus
of neon and let's fill in our electrons
everybody so one electron and then
equals one two electrons ah where are
these extra electrons going to go we
only have eight left here I had 10 minus
two equals eight electrons left well
turns out every energy level after N
equals one you can fill with eight
electrons and that is actually very
significant it actually plays its part
and naming neon as a noble gas eight
electrons it turns out is very very
suited by every single elements on the
periodic table sorry
eight electrons in the outermost shell
is very suited for just about every
element on the periodic table and that's
just because eight electrons everybody
fills its octet an act Tet is when all
valence electrons all eight this
substitute V al for valence valence
electrons fill the outermost shells on
an atom and causes it to be what we call
in chemistry and inert gas in this case
the anti gas so it is inert meaning it
cannot react with anything
readily and actually in fume hoods of
most sophisticated chemical processes
they actually use not neon but they
actually just use argon gas because it's
so darn inert it's so noble the
electrons really resist change to
anything present in that fume hood okay
so the thing to take note here is the
electrons are in defined orbitals so
notice at N equals one we have two
electrons and only two electrons at N
equals two we actually have eight
electrons and the number goes up the
more electrons you have you just keep
filling them up until you can't fill
anymore okay
so that is it I look forward to seeing
all of you tomorrow in class enjoy the
rest of your eating evening my young
think ologists have a great day