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The periodic table - classification of elements

Video transcript

this video we're going to look at the periodic table and we're going to classify the elements into groups and so as we go through these terms of going to be checking them off so the groups are the vertical columns on the periodic table and so if I go over here I can see that all of these elements are in the same vertical column so all these elements are in the same group and we call this Group one I can see that all of these elements are also in the same column right so all these elements are in the same group and we call this group two I can continue labeling my groups this would be group 3 4 5 6 7 8 9 10 11 12 and then I go back up to here and I can see I have another vertical column so group 13 14 15 16 17 and finally 18 so that's one way to number your groups there is another way to number your groups and that would be to say that group 1 is group 1 a group 2 is group 2 a and then kind of ignoring groups 3 through 12 continue on with your numbering systems a 1 a 2 a that would make this group 3 a group for a group 5 a group 6 a 7 a and finally a and the second way of numbering your groups is useful when you're thinking about valence electrons and so let's move on to the concept of periods right so a period is a horizontal row on the periodic table and so if I look at period 1 and I just move across my my periodic table right hydrogen is in the first period and so is helium I move on to the second period so lithium beryllium boron carbon nitrogen oxygen fluorine and neon and so I can continue with numbering my period so this is B period 3 4 5 & 6 now notice I don't have the entire periodic table on this video I didn't have enough room and we're not really going to talk about all the elements anyway so let's uh let's go ahead and focus on on metals next and so let's talk about the alkali metals and so when I'm talking about metals I'm going to try to to write in red here so the alkali metals are found in Group one or group one a so things like lithium and sodium potassium right so here are my alkali metals the alkali metals are soft silvery metals that are extremely reactive and one nice thing about organizing elements into groups is elements in the same group have similar chemical properties and so the alkali metals react in similar ways for example all the alkali metals will react with water and the alkali metals turn out to be so reactive that you're not gonna find them in their pure state in nature you're not gonna walk outside and find some sodium lying on the grounds okay they're found in nature in combination with other elements alright let's talk about hydrogen because hydrogen is also in Group one but hydrogen is not an alkali metal hydrogen is a nonmetal so I'm gonna go ahead and draw that in green here so I will represent nonmetals in green so hydrogen isn't is the exception in Group one next let's talk about the alkaline earth metals so you find those in Group two or group two a so right in here so things like magnesium and calcium and strontium are your alkaline earth metals your upline earth metals are reactive not quite as reactive as the metals in Group one but you don't find these in in the pure state either you find them in combination with other elements and so once again the the alkaline earth metals are going to react in similar ways they have similar chemical properties and so that's again a convenient way of organizing the periodic table into groups so for right now let's just go ahead and say it groups 3 through 12 right these are all metals in here and let's talk about metals in general for a minute so so metals the properties of metals so no metals are solids at room temperature except for mercury so here is mercury down here which is a liquid at room temperature metals are very valuable which means that you can form them in two different shapes they're very workable they're not they're not brittle metals are are also ductile which means you can draw them into wires you can form them into wires for example on copper so here's copper right here so copper wires of course carry current in in homes right so metals are good conductors of heat and electricity and so those are those are the properties of metals that most textbooks will talk about so let's let's let's contrast those with nonmetals right so nonmetals if you have a a solid nonmetal those those solids would tend to be brittle not malleable like like metals non-metals are poor conductors of heat and electricity so you find nonmetals in different states that matter so let's talk about one of the nonmetals now and that would be the halogens and so let's find let's find the halogens on our periodic table you find them in group 7a or group 17 and so things like fluorine chlorine bromine so here are your halogens right in here so halogens are very reactive non metals so they're often very colorful very very corrosive and the name halogen actually means salt former and so we're actually going to going to come back to that in the next video when we look at some electron configurations and we talk about why these things are so reactive and so those are those are the halogens next let's find the the noble gases so the noble gases are found in group 8a or group 18 so some of these are very famous like helium neon argon Krypton alright so here are your noble gases they're colorless gases and they're generally very unreactive and so once again we'll talk about why in the next video when we talk about some of electron configurations alright so there are there are some other nonmetals on here which will I will identify in a minute first I want to talk about the fact that you pretty much find metals on the left side of the periodic table alright so let me go back to the red color and you can see right I have all these metals over here on the left side and then for my nonmetals right in green you're gonna find those over here the right side of your of your periodic table and so the dividing line between those let me go ahead and draw it in there it's kind of a kind of a zigzag line so let me see if I can sketch it in here so the dividing line would go something like this all right so we're going to go as exact line down our periodic table and some of the elements that you find on this zigzag line have properties in between those of metals and nonmetals and we call those metalloids so let's go ahead and talk about metalloids now so metalloids right oh it of course being like a metal so it's similar to metals but again the properties are in between those of a metal and a nonmetal so some of the elements that are considered that are considered to be metalloids would be boron right in here so silicon germanium arsenic antimony tellurium and sometimes you'll see a Satine listed as as one so it depends on which textbook that you're looking in so you can see that some of the elements along this zigzag line are considered to be metalloids and there's no there's no official one definition for which elements are considered to be to be metalloids and so you might see you might see a little bit of you might see a little bit of a discrepancy there for some of these elements but in general those are the ones that are considered to be metalloids and silicon probably being the most famous one right so silicon is a semiconductor all right so it's a metalloid so it's like a metal so it does conduct electricity but not the same extent that a that a metal would and so these intermediate properties are sometimes useful and so let's uh let's go ahead and and Mark some of the rest of these right so these would be some other metals right and then over here on the right would be the rest of your nonmetals here so carbon is a non-metal nitrogens nonmetal oxygen is nonmetal phosphorus sulfur and so so that's just a quick way to to divide the periodic table up with some simple definitions alright so in the next video we'll talk more about the electronic structure and and we'll get into definition of transition metals