0:03 hi friends in this video we look at the
0:05 last stop in our journey the modern
0:09 periodic table remember in the previous
0:11 videos we discussed the earlier attempts
0:14 to classify elements that is the double
0:17 renews triads Newlands law of octaves
0:21 and Mendeleev spiri otic table here we
0:22 are going to look at the modern periodic
0:25 table but we are going to do it in a
0:28 different and interesting way so rather
0:30 than starting with the periodic table we
0:32 are going to start with a blank table
0:35 and will fill it up as we go along in
0:38 this video I'm sure by the end of the
0:41 video you'll be a master of the periodic
0:44 table and as usual we'll finish off with
0:48 our top three questions on this topic
0:50 normally when you draw a table it looks
0:53 something like this with rows and
0:55 columns but if you take a look at our
0:58 periodic table it has a strange shape
1:02 and we are going to see why as I said
1:04 we'll start with a blank table and we
1:06 are going to fill it up as we go along
1:09 in this video since our focus is only
1:12 till the 20th element which is calcium
1:15 so we'll be looking only at the first
1:18 four rows of the periodic table let's
1:22 call this our mini periodic table we
1:24 will talk about the lower rows later on
1:27 in this video so I'd like you to pause
1:30 the video here and go ahead and sketch
1:33 our mini periodic table in your notebook
1:36 just draw this blank table till the
1:39 fourth row you can also pause the video
1:41 here and do a print screen and take out
1:44 a printout of the blank table friends
1:46 are you ready with your blank periodic
1:49 table I'm going to magically shrink
1:51 myself so that you can see this table
1:54 better and let's fill up this table
1:58 together first let's start by numbering
2:01 the rows so it's going to be 1 2 3 and
2:05 so on in our mini periodic table we have
2:10 only 4 rows but the full table has seven
2:13 rows rows are called P
2:18 so these are period numbers similarly we
2:20 can number the columns so the column
2:23 number is going to be one two three and
2:27 all the way up to 18 columns are called
2:29 groups in the periodic table so these
2:32 are our group numbers there is a
2:34 different numbering scheme for groups as
2:37 well but we'll look at that later on in
2:38 the video
2:42 next start numbering the boxes so start
2:46 from one to finish the first row then go
2:50 on to the second row 3 4 5 and so on
2:53 these numbers look like serial numbers
2:56 or roll numbers but do you know what
2:59 they really are that's right they are
3:03 atomic numbers atomic number is defined
3:05 as the number of protons present in the
3:09 nucleus of an element this was the major
3:11 difference between the modern periodic
3:14 table and Mendeleev sporadic table
3:16 Mendeleev stable was based on atomic
3:19 mass but the modern table is based on
3:22 atomic number now you may be wondering
3:26 why because the scientist Moseley proved
3:29 that atomic number is a more fundamental
3:32 property for elements as compared to
3:35 atomic mass so the chemical properties
3:37 of elements are more related to their
3:41 atomic number than their atomic mass
3:44 next let's start filling in the elements
3:47 in our table so do you know which is the
3:49 first element with atomic number one
3:53 with just one proton in the nucleus
3:56 that's right the correct answer is
3:58 hydrogen so let's put the symbol of
4:03 hydrogen H in the first box next with
4:07 atomic number two we have helium and now
4:10 let's go down to the second row so there
4:13 we have lithium beryllium boron carbon
4:19 nitrogen oxygen fluorine and neon and I
4:22 want you to fill up all the way till
4:24 element number 20 so that is still calcium
4:26 calcium
4:28 with every element that you filled in
4:31 here the atomic number is increasing by
4:35 one so what does that mean one extra
4:38 proton is being added in the nucleus now
4:41 how is the electron number changing what
4:44 do you think that's right the electrons
4:47 are also increasing by one because
4:50 remember an atom is neutral it has equal
4:54 number of protons and electrons and note
4:56 we are not concerned about the number of
4:59 neutrons right now now let's talk about
5:01 the significance of the period or the
5:05 row so in our mini periodic table we
5:08 have periods from 1 to 4 but remember in
5:11 the full periodic table you have it up
5:14 till 7 so what is this period number
5:17 tell us it tells us the number of
5:20 electron shells or electron orbits
5:24 present in an atom so we can predict the
5:25 number of shells without even drawing
5:28 the electronic structure so let's take
5:32 some examples hydrogen is in period one
5:36 so it has only one shell now if you look
5:39 at oxygen it's in period two so it
5:43 contains two shells so similarly how
5:46 many shells does aluminium have that's
5:49 right three shells since it's in period
5:55 3 and what about calcium correct for
5:59 shells it's in period number four so
6:01 with every new period one more shell is
6:05 being added now let's verify this by
6:07 looking at the electronic configuration
6:10 of a few elements let's draw the
6:13 electron configuration of hydrogen it
6:16 has atomic number one so just one proton
6:20 and one electron and as you can see it
6:23 has only one shell next let's look at
6:26 oxygen it has atomic number eight so
6:29 that's eight protons and eight electrons
6:32 so if you draw its electron
6:34 configuration the first shell will have
6:37 two electrons since it can hold maximum
6:40 of two and the second shell has
6:44 electrons so as you can see oxygen is in
6:48 period number two and it has two shells
6:51 next we have aluminium with atomic
6:53 number thirteen so the electron
6:56 configuration is going to be 2 comma 8
6:59 comma 3 so aluminium in the third period
7:03 has 3 shells you can draw the full
7:05 electron configuration or you can write
7:08 it in this simple common notation 2
7:11 comma 8 comma 3 and let's also look at
7:13 calcium which is in the fourth period
7:16 with atomic number 20 and as you can see
7:19 it's electron configuration is 2 comma 8
7:23 comma 8 comma 2 so as expected calcium
7:27 in the fourth period has 4 shells now
7:29 let's discuss the significance of the
7:31 group we always try to group similar
7:34 things together so that it's easy for us
7:38 a simple everyday life example is the
7:40 grocery store where you'll find similar
7:43 things grouped together for example
7:45 you'll find all the vegetables together
7:49 salt and sugar on one side and all the
7:51 chocolates in one place now imagine you
7:53 walk into the grocery store and
7:56 everything is scattered you go crazy
8:00 while shopping right similarly in the
8:03 periodic table elements having similar
8:05 chemical properties are grouped together
8:10 now let's take a closer look if you look
8:14 at Group one except for hydrogen all the
8:17 elements in Group one are metals they
8:20 are called alkali metals and they have
8:22 similar chemical properties they have
8:26 the same valency one now let's look at
8:31 Group two once again we see their metals
8:34 in this group they are called alkaline
8:37 earth metals and they also have the same
8:41 valency now let's move ahead to group 17
8:43 if you look at this group
8:46 it contains nonmetals and they have the
8:49 same valency 1 now an interesting
8:52 question is why do elements in the same group
8:52 group
8:55 have same valency and similar chemical
8:59 properties what do you think well the
9:01 answer lies in how the electrons are
9:03 arranged in the atom that is the
9:07 electronic configuration so let's go
9:08 ahead and analyze the electronic
9:11 configuration of elements in the same
9:13 group let's start with the group 1
9:17 elements hydrogen lithium sodium and
9:20 potassium they have atomic numbers of 1
9:24 3 11 and 19 now let's try to write down
9:28 their electronic configuration hydrogen
9:31 is simple it just has one electron now
9:34 lithium has an atomic number of 3 so
9:37 it's going to be 2 comma 1 sodium will
9:41 be 2 comma 8 comma 1 and potassium is
9:45 going to be 2 comma 8 comma 8 comma 1 so
9:47 can you see what these elements have in
9:51 common that's right they have just one
9:54 electron in their outermost shell so
9:56 that's one valence electron so all these
9:59 elements have the valency 1 and why do
10:01 they have similar chemical properties
10:04 because chemical properties depend on
10:06 the number of valence electrons which is
10:09 same for all these elements now let's
10:12 look at Group two here we have beryllium
10:16 magnesium and calcium similarly let's
10:17 write down their electronic
10:20 configurations so beryllium with an
10:23 atomic number four is going to be 2
10:27 comma 2 magnesium which has an atomic
10:29 number of 12 the electron configuration
10:32 is going to be 2 comma 8 comma 2 and
10:35 calcium which has 20 electrons is going
10:39 to be 2 comma 8 comma 8 comma 2 so once
10:41 again you can see all these elements
10:43 have the same number of valence
10:47 electrons which is 2 in this case so
10:50 they have the same valency 2 and hence
10:54 they show similar chemical properties in
10:56 summary we saw that elements belonging
10:59 to the same group have the same valency
11:02 and similar chemical properties because
11:04 they have the same number of valence electrons
11:06 electrons
11:09 now the group numbering that we saw from
11:13 1 to 18 is the new scheme there is an
11:15 older scheme that uses Roman numbers and
11:19 alphabets a and B let's take a look at
11:22 the old scheme as well as we have seen
11:24 the new scheme has group numbers from 1
11:27 to 18 now let's look at the old scheme
11:32 Group 1 has the number 1 a note 1 is
11:35 written in Roman numeral and the
11:39 alphabet capital e group 2 is two-way
11:42 now when we go to group 3 it's tricky
11:46 it's going to be 3 B then you have 4 b5
11:53 b6 b7 B and groups 8 9 and 10 have the
11:59 Roman number 8 then group 11 is 1 b12 is
12:02 2b and then when you move on to 13 it's
12:07 3 a 4 a 5 a 6 a and group 17 is 7 a and
12:12 the last group group 18 has the number 0
12:15 the new group numbering scheme is much
12:19 easier to remember than the old one but
12:20 it's important to know the old one as
12:23 well because sometimes it's used now I
12:26 can teach you an easy trick to remember
12:28 the mapping between the new and the old
12:31 scheme basically you have to calcium in
12:35 your syllabus element number 20 so if
12:37 you take a look you have Group 1 group 2
12:43 and then group 13 14 15 16 17 and 18 in
12:46 your syllabus you don't have the groups
12:50 from 3 to 12 now if you look at the old
12:53 scheme so what you have in syllabus is 1
12:58 e2 way and then 3 a 4 a 5 a 6 a 7 a and
13:03 group 0 so basically only the a groups
13:05 are in your syllabus and group 0 which
13:09 is the noble gases the B groups and
13:12 group 8 are not in your syllabus so I
13:14 hope that helps you remember the old
13:17 scheme we have a lot of details in our
13:19 periodic table now let's go ahead and add
13:20 add
13:22 color you might have seen these colorful
13:25 pictures of the periodic table where the
13:27 colors represent the different types of
13:31 elements for example metals non-metals
13:34 noble gases and metalloids so are you
13:36 ready to start coloring our periodic
13:40 table first let's color the four broad
13:44 categories of elements metals non-metals
13:47 metalloids and noble gases
13:50 now our periodic table looks more
13:53 colorful right but you might have seen
13:55 some other periodic tables which have
13:58 more colors and some different colors in
14:00 different groups like this picture here
14:03 so let's go ahead and take a look at
14:05 some of these groups because they have
14:07 some special names the group one
14:10 elements are called alkali metals
14:13 because these form strong alkalis with
14:16 water the group two elements are called
14:19 alkaline earth metals because they form
14:22 weaker alkalis as compared to the
14:24 previous group now moving on to group
14:27 thirteen this group is called the boron
14:30 family because boron is the first member
14:34 in the group similarly group 14 is
14:36 called carbon family and then you have
14:40 group 15 as nitrogen family and group 16
14:43 is called the oxygen family or also
14:46 known as Chalco jhin's which means all
14:50 forming now group 17 is called the
14:53 halogen family and the last group group
14:56 18 are known as noble gases or inert
15:00 gases till now our focus has been from
15:05 element 1 to 20 so till calcium now
15:07 let's go ahead and take a look at the
15:10 full periodic table in the complete
15:13 periodic table we have seven periods or
15:18 seven rows and eighteen groups or 18
15:21 columns now if you look at period six
15:23 and seven you'll notice something
15:26 interesting that elements with atomic
15:31 number 57 - 71 and 89 203 are put
15:33 separately below the periodic table
15:36 this is done to compact the periodic
15:40 table the elements 57 to 71 are called
15:43 lanthanide series because they start
15:46 with the element lanthanum these
15:49 elements are rare earth elements and
15:53 elements from 89 203 are called actinide
15:56 series because they start with the
15:59 element actinium these are radioactive
16:03 elements now let's discuss the merits of
16:06 the modern periodic table the merits are
16:08 that it corrected the anomalies in
16:11 Mendeley its periodic table now how did
16:14 it do that because Mendeleev stable was
16:17 based on atomic mass but the modern
16:21 table is based on atomic number it's
16:24 based on the modern periodic law which
16:26 states that the properties of elements
16:30 are a periodic function of their atomic
16:32 number so let's take a look how the
16:35 anomalies of Mendeleev stable were
16:37 corrected first let's talk about
16:40 isotopes isotopes are atoms of an
16:43 element having same atomic number but
16:46 different mass number they have
16:49 identical chemical properties now
16:51 isotopes could not fit into Mendeleev
16:54 z-- periodic table but in the modern
16:56 periodic table they fit in nicely
16:58 because they have the same atomic number
17:02 so isotopes of an element belong in the
17:05 same position as the element and that
17:07 makes sense because they have same
17:10 chemical properties the second point is
17:12 Mendeleev had to make certain exceptions
17:15 for some elements but these are fixed in
17:18 the modern periodic table for example
17:22 the position of cobalt and nickel cobalt
17:24 should come first because it has a lower
17:27 atomic number as compared to nickel even
17:29 though it has a higher atomic mass
17:32 because the modern periodic table is
17:35 based on atomic number even though
17:37 hydrogen is placed in Group one it's
17:40 given special treatment many times it's
17:43 shown broken off from Group one now why
17:46 is that because hydrogen shows prop
17:49 that are similar to group 1 elements
17:52 that is alkali metals and also group 17
17:55 elements that is halogens so since it
17:57 shows properties of both these groups
18:01 its given special treatment friends I
18:03 hope you feel that you have mastered the
18:06 modern periodic table now remember
18:09 practice makes you perfect so I would
18:11 recommend you to draw out our mini
18:13 periodic table a couple of times and
18:17 learn the first 20 elements now trends
18:19 in the periodic table will be covered in
18:22 a separate video where we look at how
18:24 the properties change across the period
18:28 and down the group and do remember to
18:30 subscribe to my youtube channel and
18:33 follow my facebook page and do check out
18:38 my website manoj academy.com friends be
18:40 sure to try the quiz and the top three
18:43 questions for this topic links are given
