Average Atomic Mass - Atoms & Molecules, Force & Laws of Motion, Science, Class 9 Video Lecture

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what is the history of atomic mass for a
given now let's see average atomic mass
what is the average atomic mass see we
have so many isotopes of oxygen for
example 16 17 18 right so let's suppose
oxygen 16 oxygen 17 ox lady oxygen 16 is
19% and this is let's suppose point five
percent is one type person I don't know
the exact figure so I'm just putting
some values so if you talk about the
average atomic mass that means atomic
mass of any oxygen sample which you get
it will have ninety-nine percent oxygen
16 so it will have 99 by 100 into 16
plus 0.5 percent of 70 plus 0.5 percent
off so this will be the average atomic
mass because this is the average of
atomic mass of all the isotopes in the
given sample and since in the chemical
world when talk about oxygen you talk
about only oxygen it may not work oxygen
in the lab when you react example and
you burn a matchstick so their carbon is
reacting toxin you to form co2 who
discard
so that is the oxygen that is used to
burn carbon is the atmospheric oxygen
mass fraction if you see this is the
atmospheric oxygen has Oh 16 also 17
also hold in awesome right and all these
have definite nomic mass so which mass
should you take so we take average
average based on the proportion we know
oxygen 16 is 99% oxygen 17 is almost
point 5 oxygen is almost point 5 so we
take average of this and we get some
value mostly 16 point some value may be
0 to 3 and not sure of the exact value
so mallow will come and that is the
average atomic mass for oxygen similarly
for all the elements you can find the
No Mas right it is average of atomic
mass of all the isotopes available in
the nature I based on the percentage of
their availability okay now the question
is we talked about atom we talk about
size we talk about weight of that now
the question is can Adam exist
independently like a bird or any
anything which exists independently
is it possible see most of atoms they
don't exist independently they exist as
molecules and for ions molecules or ion
and this for the most but some do exist
independently for example helium argon
they all noble gas so they exist near
anything but for example if you talk
about sodium na + CL - these are
alliance you don't owe to you don't want
h2 so in this oh do we have two oxygen
atom h2 we have two hydrogen atom and
these are molecules or what are also
using okay so most of them won't exist
independently but few of them for
example helium arkin mostly noble gas
they exist independently most of the
atoms in most of the atoms exist in the
form of molecules bond ions and why
we'll study all about these in higher
classes when you talk about the
stability of ions why a sodium atom is
not stable but sodium ions stable there
reasons behind it there are reasons they
are scientific reasons for this
why chlorine atom is non stable but
chlorine mole ions is stable at 2 with a
negative charge negative charge that
means it has taken electron for non
leave it may be in the next chapter will
we talk about the atoms will touch upon
these little
but in the higher classes you will study
about these things yeah let's take some
questions here why it is not possible to
see Adam with a naked eyes see these
atoms are very small they are very small
very tiny actually and they are measured
in nanometer 10 to the power minus my
meter so small they are so small that
actually you can't see through negatives
why because see I this is also a little
advanced concept for anything to see the
way it works is you have a light
maybe sunlight already alighted light
and this object which you want to see
light will come and will get reflected
by the object and then it is reflected
by the object then your eye this is your
is me then you can see it but if the
particle is so small right then it will
not reflect the light it will just pass
through then you'll not be able to see
the object you understand this concept
in the higher classes let's understand
that this is very small so the light
will not be able to reflect the object
will not be able to reflect the light
and the salon people to see using naked
eyes will not be able to see you naked
eyes you need some high instruments
spectrometer or high quality instruments
to see this okay thank you visit our
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