all right let's talk about matter and atoms and compounds element and then we'll talk about compounds so all living things are matter so is your table or your chair or your computer matter is anything that has mass and takes up states right and NASA's a similar term to weight think about it this way we are not energy and not sort of our choices or either matter or than the energy and the my energy store matter atoms are the smallest unit of an element that retains the property of an element so what is an element an element is a type of matter that cannot be chemically converted into something else let me give you some examples so this makes a little bit more sense and one thing that I always like to do here and just start talking about the periodic table at this stage and we'll come back to this many many times so this table was put together by chemists organizing all the known elements some of these are naturally occurring some of them been especially these heavy ones have been made in the lab for example up here our lightest element is hydrogen next lightest if you read across as helium and they all are going to have you know it's 1 letter abbreviation of one or two-letter abbreviations we'll talk about that so going back to our definitions I can have an atom for example of gold and I could have an atom of carbon right and that atom of gold behaves like gold it doesn't behave like carbon an atom of carbon is still carbon anything smaller than that though no longer it's no longer gold versus no longer carbon both of these are examples of elements carbon and gold and what that means I can't take carbon and do some chemical conversions and turn it into gold which is really what a good deal of early chemistry is based on is what we now call alchemy trying to convert other things into gold and if you're dealing with a different element you can't convert one element into another element by chemical means by by reacting them say with acids or faces that sort of thing under they God there's about 92 different elements out there which is you know nice we have neon and fluorine and oxygen and all those things but that's not a lot of variety compounds are when more than one different type of atom comes together and it comes together a specific ratio something crazy found together in some way and the important thing to know about compounds is that they have different properties than the elements that form them let me give you a couple of examples a type of compound is water this is water what this chemical formula tells us is that there are two hydrogen atoms down to one oxygen atom and these chemical symbols you really want to start to get to know that H stands for hydrogen and O's dance rocks and that's sometimes you're gonna have to know it so now is a good time little too tells me that I have two hydrogen atoms this is water okay at room temperature standard pressure hydrogen is a gas as oxygen right the water isn't it has different physical and chemical properties than the atoms that form it one of my favorite examples of a compound that comes up again and again is one I already talked on the introduction sodium chloride so na is awkward abbreviation I get it first sodium they have one sodium atom and it's bound to one chlorine atom and we call it chloride and talk about that a little bit but so I have a sodium and a chloride atom that come together and this is table salt right like it tastes good put it on a lot of things sodium on its own is a metal right if I have a sodium atom in the metal and when you put this metal in water it explodes it's awesome chlorine on its own is a gas and usually it exists as seal to actually two atoms of chlorine together and it is a toxic gas if you ever hope to swimming pool you're probably familiar with that it was a little bit used in chemical warfare it's not necessarily the favorite one but it can be said it will kill you so sodium explodes in water we are essentially water so do metal chlorine is a toxic gas well you will kill you and yet table salt Pedro Regas so important point here compounds have different properties than the elements that form them