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The periodic table - classification of elements | Chemistry | Khan Academy

The periodic table - classification of elements | Chemistry | Khan Academy
this video we're going to look at the

periodic

table

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 1 I can see that all of these

elements

are also in the same column right so all these

elements

are
the periodic table   classification of elements chemistry khan academy
in the same group and we call this group too 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 two is group 2a 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 ate 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 one 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 three four five and six 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 1a 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 these

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 going to find them in
their pure state in nature you're not going to walk outside and find some sodium lying on the ground okay they're found in nature in combination with other

elements

all right let's talk about hydrogen because hydrogen is also in Group one but hydrogen is not an alkali metal hydrogen is a non metals I'm going to go ahead and draw that in green here so I will represent non metals in green so hydrogen isn't is the exception in Group one next let's talk about the alkaline
the periodic table   classification of elements chemistry khan academy
earth metals so you find those in group two or group 2a so right in here so things like magnesium and calcium and strontium are your alkaline earth metals your appt line 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 groups 3 through 12 right these are all metals in here and let's so this is talk about metals in general for a minute so so metals the properties of metals so 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 you 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 a 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 that most textbooks will talk about so let's let's uh 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 nonmetals are poor conductors of heat and electricity so you find non metals 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 7 a 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
the periodic table   classification of elements chemistry khan academy
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 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

right 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 going to find those over here on 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 lines 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 a cig zag 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 o 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 sateen
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 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 wood 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 non metals here so carbon is a non-metal
nitrogens nonmetal oxygen is not metal 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 transition metals