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the first I guess you could say modern conception of an acid in base comes from this gentleman right over here Svante Arrhenius and he was actually the third recipient of the Nobel Prize in Chemistry in 1903 and his definition of acids under under his definition of acids and bases an acid is something that increases the concentration increases increases the concentration concentration of hydrogen protons we could say protons when when put in an aqueous solution when in aqueous aqueous solution that's just a water solution and then you could imagine what a base would be you could think well maybe it basically something that decreases the protons and that's one way to think about it or you could say or you could say it decreases actually let me write this it increases it increases it increases the hydroxide concentration it increases the hydroxide concentration concentration when put in aqueous solution when in aqueous aqueous solution so let's make that concrete let's look at some examples so a strong Arrhenius acid and actually this would be a strong acid by other definitions as well would be hydrochloric acid hydrochloric acid you put it in an aqueous solution so that's the hydrogen you have the chlorine you put it in an aqueous solution you put it in an aqueous solution it will readily disassociate this is a this this reaction occurs it strongly favors moving from the left to right you're going to have the chlorine strip off the the two electrons in the covalent bond with the hydrogen leaving the hydrogen with no electrons so the hydrogen is just going to be left as a hydrogen proton and then the chlorine the chlorine has just AB that electron it had the electrons that had before and then it just nabbed an electron from the hydrogen and so it now has a negative charge and these are both in aqueous solution still it's still they're still both dissolved in the water and so you see very clearly here you put this in an aqueous solution you're going to increase the amount of you're going to increase the amount of hydrogen ions the amount of protons in the solution and we've talked about this before you'll often see a reaction written like this but the hydrogen protons that are still sit there by themselves in the water they're going to they are going to bond with the water molecules to actually form hydronium so another way that you will often see this is like this you have the hydrochloric acid hydrochloric acid it's in an aqueous solution just a fancy way of saying it's dissolved in the water and then you have the h2o you have the water molecules h2o and you'll sometimes see written okay what's in its liquid form and it's going to yield instead of just saying that you have a hydrogen ion right over here you'll say okay you know that thing that thing that the hydrogen is actually going to get bonded to a water molecule and so what you're going to be left with is actually h3o h3h3 oh now this thing this was a water molecule and all it got was a hydrogen ion that all that is is a proton it didn't come with any electrons so now this is going to have a positive charge it's going to have a positive charge and we can now say that this is going to be in an aqueous solution hydronium is going to be in an aqueous solution and you're going to have plus now you're going to still have the chloride ion or some negative ions we call it an ion chloride chloride anion and this is still this is still in an aqueous solution it is dissolved in water and remember all that happened here is that the chlorine here took all of the electrons leaving hydrogen with none then that hydrogen proton gets nabbed by a water molecule and becomes a hydronium so even by this definition you might say it increases the concentration of hydrogen protons you could say it increases the concentration of hydronium of hydronium right over here I hydronium ions so that makes by the Arrhenius definition that makes hydrochloric acid a strong acid that makes it a that makes it a strong that makes it a strong acid now what would be a strong base by the arena Stefan ition of acids and bases well one would be sodium hydroxide so let me write that down so if I have sodium hydroxide sodium na that's the sodium and then I have the hydroxide that's an oxygen bonded to a hydrogen so that's sodium hydroxide and actually if you wanted to see what this molecule looked like you have a oxygen having a covalent bond to a hydrogen let me do these in different colors oxygen has a covalent bond to a hydrogen to a hydrogen right over here and it actually has it actually has three lone pairs it actually has three lone pairs right over here it's actually nabbed an electron from from somebody someplace and so it's going to have a negative charge it is going to have a negative charge X I can write it well let me just write it like that it has a negative charge and then you have a sodium you have a sodium ion that has lost its electron somehow so you have a sodium ion that has lost an electron somehow so it has a positive charge and for all we know it could have lost the electron to to the oxygen right over here making the oxygen negative and making the sodium positive and so this is now positive this is negative they're going to be attracted to each other and they form an ionic bond so sodium hydroxide they have an ionic bond because the sodium is actually positive and the hydroxide part right over here that is that is negative and that's what draws them together but anyway you put this in an aqueous solution you throw some sodium hydroxide into an aqueous solution it will disassociate into into sodium with its positive charge the sodium ions and actually you know the sodium ion is still part of this that's what makes it attracted to the hydroxide anion but it's still going to be in an aqueous solution and then you're going to have the hydroxide you're going to have the hydroxide anion so essentially this thing just disassociates this has a negative charge and it's still going to be dissolved in the water so aqueous solution so you throw sodium hydroxide in water it's going to increase the concentration it's going to increase the concentration of hydroxide in the water it's going to increase the hydroxide concentration and so by the arena Stefan ition of acids and bases this would be a strong or aeneas base this would be a strong strong base by the arena Stefan ition now and I encourage you to to look at that relative to the other definitions the bronsted-lowry definition of acids and bases and the Lewis definition of acids and bases and see how you would think about categorizing things