Periodic Table Explained: Introduction
in the first video we saw that all the things in the world are made of incredibly tiny particles called atoms and also that there are 92 different kinds of them most things have more than one kind of atom in them but this nugget of pure gold contains only gold atoms so we call it an element an element is a substance made of only one kind of atom zooming back out we see that the gold atoms become a lump of gold again if we zoomed out from silver atoms we'd see a lump of silver instead because there are 92 kinds of atoms there must be 92 elements - one for each kind you probably have already heard of some of them like carbon iron and aluminium or aluminum if you're American but maybe not astatine or you terbium with so many elements there's a lot of names to remember fortunately there's a list showing all the elements it starts with the element with the lightest atoms hydrogen and goes to the element with the heaviest items uranium this list is called the
tablehow about grabbing your own copy now and check it as you watch the video the lightest element hydrogen is at the top left-hand side of the
tableeach element can be written with a shorthand using one or two letters called its symbol which is capital H for hydrogen not surprisingly each element also has its own number showing its place in this list called it's atomic number hydrogen is the lightest element so it's atomic number is 1 zooming into helium at the top right we can see that...
it's symbol is h-e-b gage fiddly to make it a bit different two hydrogen's and it's atomic number is two being the second lightest element the third lightest element is lithium so it has an atomic number of three where's lithium it starts the next row this row goes up to atomic number ten before another row is started how many rows are they one two three four five six seven the
tablehas seven horizontal rows what about these rows down below called the lanthanides and actinides well they really belong to row six and seven and should slot into these spaces the lanthanides are elements 5771 and the actinides are elements 89 to 103 - slot them in we have to make the
tablewider this full
tableis more accurate and some versions are printed this way this layout also makes it easier to see how many elements are in each row 2 in the first row 8 in the second eight in the third 18 in the fourth 18 also in the fifth 32 and the sixth 32 and the seventh altogether there are 118 elements hc' how come on the meant-to-be airline 92 elements with uranium being the last one yes but clever scientists have made artificial elements in the lab like neptunium and plutonium the elements next door that were made in 1940 these new elements make the overall list of elements a bit longer let's collapse the
tableback to its usual shape which is more convenient for fitting onto the screen you can see that the
tableis also arranged in...
vertical columns which scientists call groups how many groups are there one two three four five six seven eight nine ten eighteen eighteen vertical groups the key point about groups is that they contain elements that are similar to each other like members of a family for example all of group 1 elements except hydrogen are soft malleable metals that explode when you put them into water some groups even have family names group 1 elements are called the alkali metals group 2 elements are the alkaline earth metals group 17 are the halogens and group 18 other noble gases now you're ready to read the
tablewhat is the name of the element with atomic number 30 you just have to scan around and find 30 Zink what is the atomic number of calcium now you've got to find calcium on the
table20 which row is sulfur in the third row choose any element in the fifth row there are a lot of possible answers for this could be strontium tin iodine you choose which group is chlorine in group 17 choose an element in group 15 could be nitrogen or arsenic or any of the others your choice but what if you were asked which element is in row five and group two there can only be one answer strontium each element has its own unique combination of row and group can you see the gray diagonal band that splits the
tableinto two parts this divides the elements into metals on the left and nonmetals on the right what is a metal here's a few titanium iron chromium aluminum silver and...
gold with the atomic numbers above the symbols have you noticed that these metals are shiny and solid they all are well except for liquid mercury metals also conduct electricity and heat here the different metals are connected to an electrical circuit if the bulb lights up it means that the thing is an electrical conductor they all are medals are also malleable which means that if you built them with a hammer they'll flatten into a thinner shape here you can see that aluminium has three metallic properties it's already been flattened into a thin sheet it's shiny and it conducts electricity we looked at aluminium titanium chromium iron silver and gold all to the left of the diagonal and saw that they all have metallic properties what about nonmetals to the right hand side of the diagonal they're the opposite most nonmetal elements are liquids or gases but there are a few solids and these can be more easily tested here sulfur and selenium are showing that they don't conduct electricity can you see that the bulb doesn't light up and if you hit this carbon with a hammer it smashes into bits this is called being brittle it's the opposite of being malleable let's use the
tableto predict whether an element would be a metal or a nonmetal how about osmium atomic number 76 osmium is to the left of the diagonal gray band so it should be a metal how about iodine that's to the right of the diagonal line so it's a nonmetal let's try...
something tricky Oh do you reckon yttrium atomic number 39 would be shiny it's to the left of the diagonal line so it's a metal so it's probably shiny would phosphorous atomic number 15 conduct electricity hmm it's to the right of the diagonal so it's a nonmetal probably not what about the elements inside the diagonal band let's take a look at silicon it looks shiny like a metal but if you whack it with a hammer it breaks into bits so it's brittle like a nonmetal and the dull glow of the bulb tells us that it conducts electricity more than a nonmetal but not as much as a metal and this gives it the name of semiconductor these elements are also called semi metals because they have properties that are in between metals and nonmetals are they more metal or nonmetal elements metals nearly three-quarters of the elements on the
tableare metals but that doesn't mean they're more abundant because in the Earth's crust there are more oxygen and silicon atoms than the rest combined and the universe as a whole is mostly hydrogen in fact hydrogen is special in lots of ways it's to the left of the diagonal but it's not a metal well it can't be it's a gas it looks like it's in Group one as a member of the alkali metals but it can't be because it's not a metal the truth is hydrogen doesn't belong to any group and it's considered to be a group all by itself some
tables even put it on its own to show...
this just remember hydrogen is special the