The video explains the structure and fundamental principles of the modern periodic table by building a "mini" version from scratch, focusing on the first 20 elements and their atomic numbers, periods, and groups. It highlights how atomic number, rather than atomic mass, is the basis for element classification and how this leads to a more consistent arrangement of elements with similar properties.
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hi friends in this video we look at the
last stop in our journey the modern
periodic table remember in the previous
videos we discussed the earlier attempts
to classify elements that is the double
renews triads Newlands law of octaves
and Mendeleev spiri otic table here we
are going to look at the modern periodic
table but we are going to do it in a
different and interesting way so rather
than starting with the periodic table we
are going to start with a blank table
and will fill it up as we go along in
this video I'm sure by the end of the
video you'll be a master of the periodic
table and as usual we'll finish off with
our top three questions on this topic
normally when you draw a table it looks
something like this with rows and
columns but if you take a look at our
periodic table it has a strange shape
and we are going to see why as I said
we'll start with a blank table and we
are going to fill it up as we go along
in this video since our focus is only
till the 20th element which is calcium
so we'll be looking only at the first
four rows of the periodic table let's
call this our mini periodic table we
will talk about the lower rows later on
in this video so I'd like you to pause
the video here and go ahead and sketch
our mini periodic table in your notebook
just draw this blank table till the
fourth row you can also pause the video
here and do a print screen and take out
a printout of the blank table friends
are you ready with your blank periodic
table I'm going to magically shrink
myself so that you can see this table
better and let's fill up this table
together first let's start by numbering
the rows so it's going to be 1 2 3 and
so on in our mini periodic table we have
only 4 rows but the full table has seven
rows rows are called P
so these are period numbers similarly we
can number the columns so the column
number is going to be one two three and
all the way up to 18 columns are called
groups in the periodic table so these
are our group numbers there is a
different numbering scheme for groups as
well but we'll look at that later on in
the video
next start numbering the boxes so start
from one to finish the first row then go
on to the second row 3 4 5 and so on
these numbers look like serial numbers
or roll numbers but do you know what
they really are that's right they are
atomic numbers atomic number is defined
as the number of protons present in the
nucleus of an element this was the major
difference between the modern periodic
table and Mendeleev sporadic table
Mendeleev stable was based on atomic
mass but the modern table is based on
atomic number now you may be wondering
why because the scientist Moseley proved
that atomic number is a more fundamental
property for elements as compared to
atomic mass so the chemical properties
of elements are more related to their
atomic number than their atomic mass
next let's start filling in the elements
in our table so do you know which is the
first element with atomic number one
with just one proton in the nucleus
that's right the correct answer is
hydrogen so let's put the symbol of
hydrogen H in the first box next with
atomic number two we have helium and now
let's go down to the second row so there
we have lithium beryllium boron carbon
nitrogen oxygen fluorine and neon and I
want you to fill up all the way till
element number 20 so that is still calcium
calcium
with every element that you filled in
here the atomic number is increasing by
one so what does that mean one extra
proton is being added in the nucleus now
how is the electron number changing what
do you think that's right the electrons
are also increasing by one because
remember an atom is neutral it has equal
number of protons and electrons and note
we are not concerned about the number of
neutrons right now now let's talk about
the significance of the period or the
row so in our mini periodic table we
have periods from 1 to 4 but remember in
the full periodic table you have it up
till 7 so what is this period number
tell us it tells us the number of
electron shells or electron orbits
present in an atom so we can predict the
number of shells without even drawing
the electronic structure so let's take
some examples hydrogen is in period one
so it has only one shell now if you look
at oxygen it's in period two so it
contains two shells so similarly how
many shells does aluminium have that's
right three shells since it's in period
3 and what about calcium correct for
shells it's in period number four so
with every new period one more shell is
being added now let's verify this by
looking at the electronic configuration
of a few elements let's draw the
electron configuration of hydrogen it
has atomic number one so just one proton
and one electron and as you can see it
has only one shell next let's look at
oxygen it has atomic number eight so
that's eight protons and eight electrons
so if you draw its electron
configuration the first shell will have
two electrons since it can hold maximum
of two and the second shell has
electrons so as you can see oxygen is in
period number two and it has two shells
next we have aluminium with atomic
number thirteen so the electron
configuration is going to be 2 comma 8
comma 3 so aluminium in the third period
has 3 shells you can draw the full
electron configuration or you can write
it in this simple common notation 2
comma 8 comma 3 and let's also look at
calcium which is in the fourth period
with atomic number 20 and as you can see
it's electron configuration is 2 comma 8
comma 8 comma 2 so as expected calcium
in the fourth period has 4 shells now
let's discuss the significance of the
group we always try to group similar
things together so that it's easy for us
a simple everyday life example is the
grocery store where you'll find similar
things grouped together for example
you'll find all the vegetables together
salt and sugar on one side and all the
chocolates in one place now imagine you
walk into the grocery store and
everything is scattered you go crazy
while shopping right similarly in the
periodic table elements having similar
chemical properties are grouped together
now let's take a closer look if you look
at Group one except for hydrogen all the
elements in Group one are metals they
are called alkali metals and they have
similar chemical properties they have
the same valency one now let's look at
Group two once again we see their metals
in this group they are called alkaline
earth metals and they also have the same
valency now let's move ahead to group 17
if you look at this group
it contains nonmetals and they have the
same valency 1 now an interesting
question is why do elements in the same group
group
have same valency and similar chemical
properties what do you think well the
answer lies in how the electrons are
arranged in the atom that is the
electronic configuration so let's go
ahead and analyze the electronic
configuration of elements in the same
group let's start with the group 1
elements hydrogen lithium sodium and
potassium they have atomic numbers of 1
3 11 and 19 now let's try to write down
their electronic configuration hydrogen
is simple it just has one electron now
lithium has an atomic number of 3 so
it's going to be 2 comma 1 sodium will
be 2 comma 8 comma 1 and potassium is
going to be 2 comma 8 comma 8 comma 1 so
can you see what these elements have in
common that's right they have just one
electron in their outermost shell so
that's one valence electron so all these
elements have the valency 1 and why do
they have similar chemical properties
because chemical properties depend on
the number of valence electrons which is
same for all these elements now let's
look at Group two here we have beryllium
magnesium and calcium similarly let's
write down their electronic
configurations so beryllium with an
atomic number four is going to be 2
comma 2 magnesium which has an atomic
number of 12 the electron configuration
is going to be 2 comma 8 comma 2 and
calcium which has 20 electrons is going
to be 2 comma 8 comma 8 comma 2 so once
again you can see all these elements
have the same number of valence
electrons which is 2 in this case so
they have the same valency 2 and hence
they show similar chemical properties in
summary we saw that elements belonging
to the same group have the same valency
and similar chemical properties because
they have the same number of valence electrons
electrons
now the group numbering that we saw from
1 to 18 is the new scheme there is an
older scheme that uses Roman numbers and
alphabets a and B let's take a look at
the old scheme as well as we have seen
the new scheme has group numbers from 1
to 18 now let's look at the old scheme
Group 1 has the number 1 a note 1 is
written in Roman numeral and the
alphabet capital e group 2 is two-way
now when we go to group 3 it's tricky
it's going to be 3 B then you have 4 b5
b6 b7 B and groups 8 9 and 10 have the
Roman number 8 then group 11 is 1 b12 is
2b and then when you move on to 13 it's
3 a 4 a 5 a 6 a and group 17 is 7 a and
the last group group 18 has the number 0
the new group numbering scheme is much
easier to remember than the old one but
it's important to know the old one as
well because sometimes it's used now I
can teach you an easy trick to remember
the mapping between the new and the old
scheme basically you have to calcium in
your syllabus element number 20 so if
you take a look you have Group 1 group 2
and then group 13 14 15 16 17 and 18 in
your syllabus you don't have the groups
from 3 to 12 now if you look at the old
scheme so what you have in syllabus is 1
e2 way and then 3 a 4 a 5 a 6 a 7 a and
group 0 so basically only the a groups
are in your syllabus and group 0 which
is the noble gases the B groups and
group 8 are not in your syllabus so I
hope that helps you remember the old
scheme we have a lot of details in our
periodic table now let's go ahead and add
add
color you might have seen these colorful
pictures of the periodic table where the
colors represent the different types of
elements for example metals non-metals
noble gases and metalloids so are you
ready to start coloring our periodic
table first let's color the four broad
categories of elements metals non-metals
metalloids and noble gases
now our periodic table looks more
colorful right but you might have seen
some other periodic tables which have
more colors and some different colors in
different groups like this picture here
so let's go ahead and take a look at
some of these groups because they have
some special names the group one
elements are called alkali metals
because these form strong alkalis with
water the group two elements are called
alkaline earth metals because they form
weaker alkalis as compared to the
previous group now moving on to group
thirteen this group is called the boron
family because boron is the first member
in the group similarly group 14 is
called carbon family and then you have
group 15 as nitrogen family and group 16
is called the oxygen family or also
known as Chalco jhin's which means all
forming now group 17 is called the
halogen family and the last group group
18 are known as noble gases or inert
gases till now our focus has been from
element 1 to 20 so till calcium now
let's go ahead and take a look at the
full periodic table in the complete
periodic table we have seven periods or
seven rows and eighteen groups or 18
columns now if you look at period six
and seven you'll notice something
interesting that elements with atomic
number 57 - 71 and 89 203 are put
separately below the periodic table
this is done to compact the periodic
table the elements 57 to 71 are called
lanthanide series because they start
with the element lanthanum these
elements are rare earth elements and
elements from 89 203 are called actinide
series because they start with the
element actinium these are radioactive
elements now let's discuss the merits of
the modern periodic table the merits are
that it corrected the anomalies in
Mendeley its periodic table now how did
it do that because Mendeleev stable was
based on atomic mass but the modern
table is based on atomic number it's
based on the modern periodic law which
states that the properties of elements
are a periodic function of their atomic
number so let's take a look how the
anomalies of Mendeleev stable were
corrected first let's talk about
isotopes isotopes are atoms of an
element having same atomic number but
different mass number they have
identical chemical properties now
isotopes could not fit into Mendeleev
z-- periodic table but in the modern
periodic table they fit in nicely
because they have the same atomic number
so isotopes of an element belong in the
same position as the element and that
makes sense because they have same
chemical properties the second point is
Mendeleev had to make certain exceptions
for some elements but these are fixed in
the modern periodic table for example
the position of cobalt and nickel cobalt
should come first because it has a lower
atomic number as compared to nickel even
though it has a higher atomic mass
because the modern periodic table is
based on atomic number even though
hydrogen is placed in Group one it's
given special treatment many times it's
shown broken off from Group one now why
is that because hydrogen shows prop
that are similar to group 1 elements
that is alkali metals and also group 17
elements that is halogens so since it
shows properties of both these groups
its given special treatment friends I
hope you feel that you have mastered the
modern periodic table now remember
practice makes you perfect so I would
recommend you to draw out our mini
periodic table a couple of times and
learn the first 20 elements now trends
in the periodic table will be covered in
a separate video where we look at how
the properties change across the period
and down the group and do remember to
subscribe to my youtube channel and
follow my facebook page and do check out
my website manoj academy.com friends be
sure to try the quiz and the top three
questions for this topic links are given
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