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 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 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 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 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 below the video thanks for watching