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Homologous series again this is the one
which had made a classification in
cooke in the classification of
the table so let us know what is
actually cooke for moving the scenes
so the basis of physical and chemical
properties
cooke classsifield elements in several homologous
 so what is it a whole another
series of it that we talked about that
also so cook also found that the atomic
weight of the element in homologous in
the series increases in a regular
fashion so this is what i am going to
talk about then it also had made a
statement once it has represented the
official population chemical properties
of the group of elements that has been
kept in the cooke's  homologous of the series as
well as the an atomic number shows will
be increasing as we as we pull from in a
group that is from Opteron and because
also that the atomic number atomic
weight increases and because this kind
of arrangement that it has made you know
one of the cities it had a particular
section on it had a particular time then
it has shown in this series and also
this is one of the groups that area as
you can see in the screen it is it is X
we go from nitrogen phosphorus arsenic
antimony and bismuth so all has an
atomic weight of 40 50 175 as we go see
14:31 75 119 and two zero seven so this
economic weights are not only published
in all these groups are gonna be rich in
the matter of the chemical property but
yes the pattern is the end of diamond
what is that let me show you first
if 14 here is a atomic weight of
nitrogen so for that suppose the actions
we can make it as a but the next element
after the nitrogen when it comes to
group so it is phosphorus that is having
a atomic weight of 31 so that could be
distributed in 14 plus 70 so as to make
red even so even that is can be written
as a plus P but again if we talk about
arsenic arsenic has an atomic weight of
75 so that can be written as fourteen
plus seventy plus 42 that is a plus B
plus C so this is the homologous is what
we have been right
what we have to do it as the 14 is the
one which is been repeated in each and
every element if we cross from nine
different to this one so this is the one
that is been the same over I am talking
about the 17 1917 is the one which is
again repeating so this is showing that
this has a regular pattern or has it but
you are sequence so ice to make the
atomic theory of a particular element
and okay for the next one that is
arsenic it is 40 plus 17 plus 24 that is
nothing but can be written as a plus B
plus C but I am talking about the
antimony that is it is has an atomic
weight of 119 so we could write it as 40
the 17 + e really but now this akkadian
is nothing but the double of the 44 that
is can be written as 2 C so therefore it
is has a regular matter of 8 plus B plus
2 C and talking about the last one that
is for bismuth it is nothing but having
an atomic mass of 7 so again that could
be written with a hole in the series
that we have got that is 4 equal to the
common thing okay 17 would be the common
weight my in 170 C is nothing but we for
dex that of the 88
so therefore or 4 times that of the 44
so therefore we could write it as a plus
B plus 4c so this is what it repeats in
a regular fashion as seeds
so therefore this was made by the hoops
homologous and this is known as the
series which is beta value in but even
that had any limitation that it is not
waiting for everything but this is what
we have mean so thank you friends for
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