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hey kiddos today we're gonna talk about
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valence and ions we've been talking for
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the past few videos about electrons and
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electron configurations and we mentioned
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at the beginning of that that electrons
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are really the heart of everything that
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happens in chemistry that chemical
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reactions happen because of things that
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happen with electrons and more
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specifically what is really at the heart
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of 90% of chemistry 95% 98% I don't know
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I'm just making up numbers a large
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percentage of chemistry is what happens
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with valence electrons valence electrons
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by and large are the electrons that
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perform reactions the ones that are
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going to form ions that we're gonna show
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today the ones that obviously there's
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ions are going to lead to ionic bonds
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the electrons that are shared in the
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formation of covalent bonds the
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electrons that form up the something the
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majority of the sea of electrons and
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metallic bonds everything there comes
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down to our valence electrons so what
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are valence electrons and most of you
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probably talked a little bit about
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valence electrons in middle school
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remember that your valence electrons are
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your electrons in your outermost energy
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level and so if we drew these things
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according to a Bohr model and of course
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we don't draw things according to Bohr
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model most of the time but we'll talk
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about the electron configuration here in
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a little bit but on your Bohr model your
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outermost energy level so sodium nucleus
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here I've got first energy level second
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energy level first level is completely
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full second level is completely full
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third level has one electron in it so
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what we would say then is that for the
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sodium that in its normal natural state
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this sodium with all of its normal
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eleven electrons which is what we have
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here
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sodium has one valence electron if we
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look over here at this fluorine we can
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see the fluorine has seven valence
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electrons because its highest energy
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level as the second energy level okay so
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two in the first level seven in the
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second so how do we know how many
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valence electrons there without drawing
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that out or without drawing out the
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electron configuration that we'll do
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here in a second what's actually pretty
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simple if you look at the periodic table
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here you'll notice I didn't put in the
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f-block we're gonna we're not gonna
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worry too much about the f-block or
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really even the d-block right now
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because for everything that we're gonna
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do in chem 1 what matters for valence is
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what's in the s and P and we'll you'll
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see why here in just
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so the way that we would typically find
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how many valence electrons are in
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something is that we would look at the
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periodic table we would start over here
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on the left hand side of the periodic
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table and we would count until we get to
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our element
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specifically we don't count every box we
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count the boxes that are just in the s
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and P orbitals in other words we're
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gonna skip the D orbital okay so what
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does that mean well if I'm doing sodium
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sodium's in the first column so it has
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one valence electron that's pretty
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straightforward if we were over here
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doing fluorine we would say we have one
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two three four five six seven valence
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electrons if you were going to neon
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which is next to fluorine it's got one
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two three four five six seven eight
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valence electrons okay well what what if
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you were down here lower in the table
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and you were down say and there were
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d-block stuff in the way what if you
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were down here at say bromine or
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something like that well you would do
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the same principle all the only thing
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that would be different is that you're
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gonna skip the d-block so I'm gonna go 1
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2 3 4 5 6 7 now what you'll notice is
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that bromine - the same column as
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fluorine
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they're gonna have the same number of
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valence electrons they're gonna have the
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same ending electron configuration and
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in fact to go back to what we already
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know about the periodic table this is
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what actually the periodic table is set
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up on we said that it set up according
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to atomic number which it is but atomic
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number is what leads us into the number
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of electrons that something has we also
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said that the periodic table is set up
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according to properties which it is but
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the properties are largely determined by
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their valence electrons because the
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valence electrons the number of valence
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electrons that they have the electrons
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in the outermost energy level are what
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actually determined how they react and
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what their properties are okay and so
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the periodic table really although we
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say that it's set up by atomic number
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and by properties which is true both of
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those things essentially come back to
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one thing which is electrons and
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specifically valence electrons that's
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how we set up the periodic table that's
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why everything is sort of lined up in
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the way that it is that gives you sort
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of the easy way to tell immediately what
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the valence
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where is for any given atom and the way
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that we do that is you'll notice that if
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you look at a periodic table that the
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groups of the periodic table were sort
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of numbered one two three four all the
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way over to 18
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okay so noble gases are group eighteen
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but if you're looking at a good periodic
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table what you probably also noticed is
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that they were given Roman numerals as
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well and so you had one A two A three a
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and then if you look through here you
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would see B well here's the trick since
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you're only worried about s and PS four
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valence electrons and again I'm going to
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show you the electron configurations
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here in a second you'll see why since
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you're only concerned about SNPs you're
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just counting across there's really only
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eight possibilities there and the group
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a elements the ones that have a after
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the Roman numerals the number in front
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of them just tells you what the valence
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is and so this over here is eight a and
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so eight a tells me since that's a group
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a tells me that all of the noble gases
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have eight valence electrons with that
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one obvious exception of helium we
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already started to talk about helium
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helium goes over here because it behaves
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like a noble gas but electron
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configuration wise it goes here because
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it ends in s right okay so and again
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there are some exceptions in chemistry
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but that's generally how it works
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so you can just sort of immediately know
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look at the column that they're in and
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know how many valence electrons there
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and if you know the first couple of rows
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pretty well which you will because
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you'll work a lot with oxygen and carbon
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and nitrogen and those things then
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you'll know that hey um so oxygen is
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here nitrogen is here so a nitrogen let
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me write that in real quick so you see
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where we're going so nitrogen is one two
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three four five
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that means everything in that column is
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five so the phosphorous below it also
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has five valence electrons the arsenic
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below that also has five valence
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electrons everything in the same column
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has the same number of valence electrons
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let's find that in real quick to our
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electron configurations as well so if we
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were out our electron configuration out
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for sodium we would have one s two okay
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1 s 2 s 2 2 P 6 ok so we did 2 s 2 2 P
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we filled that up and then we end over
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here at 3s1
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so what's the highest energy level
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remember that your energy levels are the
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coefficients right okay so my highest
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energy level is three how many electrons
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are in that energy level we'll just the
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one the one in the 3s what about over
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here for fluorine well let's write our
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electron configuration for that real
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quick 1s2 2s2 2p5 okay how do they get
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there 1s2 2s2 2p1
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two three four five so that becomes that
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what's the highest energy level well in
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this case it's two is the highest energy
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level not the highest sublevel but the
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highest energy level and so that means
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that I'm going to add up both of those
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twos together I'm gonna add two plus
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five which gives me seven which is how
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many valence electrons I have in
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fluorine so how do you find the number
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of valence electrons you count from left
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to right or if you have an electron
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configuration you look at your highest
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energy level okay and you take all of
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those together and that becomes your
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valence electrons
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your shouldn't and if you ever get a
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case where you've got more than eight
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valence electrons you have done
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something terribly terribly wrong
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there's only eight possibilities because
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there's only two s columns and six P
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columns and so those two together add up
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to be eight so how does all of that lead
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us then to how does all the stuff that
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we just talked about with valence and
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how to count across and look at the
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order look at the electron configuration
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and find out the valence electrons how
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does all of that then lead us into ions
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and bonding and that stability that
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we're looking well everything as far as
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stability for atoms comes down to the
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fact that the most stable state is what
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we call the ng EC the ng EC is the noble
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gas electron configuration and what that
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means is that there we're gonna the
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atoms are gonna try to change themselves
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in such a way they're gonna move their
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electrons around in such a way so that
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they all end up with doable gas electron
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configuration you might have heard
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teachers say that they want to have a
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certain number of electrons usually
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eight okay because that's a full octet
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that's the octet rule it doesn't have to
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be
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obviously helium only has two and so
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hydrogen and helium aren't trying to get
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to eight they can't hold eight they were
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only in the first level the first level
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won't hold eight and so they're trying
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to get to two essentially everything is
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more stable when it has a noble gas
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electron configuration when we say
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they're trying to get to something or
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they want something obviously that's not
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the case
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it's a more stable situation if they
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have a noble gas electron configuration
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that's why that's why noble gases are
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noble gases because they're really
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stable and therefore they don't want to
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react with things so noble gas electron
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configuration is what they're shooting
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for okay well in this case neither of
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these two things have a noble gas
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electron configuration right now for
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increased stability it would be more
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beneficial if they did something that
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either added or removed electrons or
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we'll see you later when we do covalent
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bonding if they shared electrons in some
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way so that they could then get to a
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noble gas electron configuration so
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here's the way that that's going to work
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things on the left-hand side of the
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staircase the metals metals tend to give
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up their electrons their valence
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electrons they get rid of their
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electrons because usually and pretty
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much all of those cases they're gonna
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have four or less valence electrons and
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so if they get rid of their electrons
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that will make them more stable and I'll
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show you how that works here in a second
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for nonmetals things to the right of the
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staircase they're going to tend to gain
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electrons okay because it tends to be
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most the time that they have four or
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over electrons already and so it's a lot
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closer for them to gain electrons to get
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to the eight that gives them the noble
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gas core or the noble gas electron
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configuration that's in general what is
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an easier to achieve stability than to
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lose them okay so metals are going to
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lose electrons nonmetals are going to
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gain electrons that's going to lead us
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into two different types of ions so
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let's look at how that happens so sodium
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we said is a metal obviously sodium has
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one valence electron right there you can
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see it right there it's the electron in
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three s1 fluorine has seven valence
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electrons okay and remember that what
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we're sort of shooting for
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here is our good friend the octet rule
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okay
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the octet rule is basically a fancy way
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of saying noble gas electron
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configuration the octet rule says that
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for increased stability the atoms are
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going to try to have eight valence
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electrons and again with the exception
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there are hydrogen and helium those can
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make some exceptions lithium is going to
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be an exception as well the really small
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ones are exceptions they're gonna try to
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get two noble gas electron configuration
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and most of the time that means having
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eight valence electrons so how can I get
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to that well this sodium has one and we
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said that metals are going to lose lose
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their electrons and so what I'm going to
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do is I'm going to remove that one
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valence electron there okay if I remove
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that one valence electron then what I'm
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also doing is I'm removing it here as
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well right
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that's what I removed was that three s
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one electron and now I have a situation
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where level three is no longer my
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highest occupied energy level this
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outermost level here it's not occupied
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there are no electrons in it my highest
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occupied energy level in the sodium now
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is here and as you can see we have eight
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electrons you could see it there and you
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can see it if you look at the electron
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configurations energy level two is now
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my actual highest occupied energy level
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and there are two plus six is eight
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valence electrons now okay and what's
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really cool here is we said that we're
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trying to get the noble gas electron
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configuration
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well what noble gas does that get us to
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well that gets us to our good buddy neon
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over here neon has an electron
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configuration of 1s2 2s2 2p6 highest
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energy levels to eight electrons you'll
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notice that that is the exact same thing
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as this sodium is after it loses its
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electron now once it loses its electron
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it is no longer a simple everyday sodium
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it is now a sodium ion specifically it
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has an na plus now why is it have a plus
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seems really weird that you would lose
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something lose an electron and then get
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a positive charge well remember
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electrons have a negative charge right
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and so if you lose a negative that makes
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you more positive think about your own
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attitude if you've got a bad attitude on
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a day and somehow you lost the
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negativity then you would be more
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positive right and so that's exactly
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what happens we can explain that in
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terms of protons and electrons as well
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sodium has 11 protons which means 11
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positive charges it had 11 negative
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charges but we removed one of them so
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now it only has 10 negative charges and
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so if we add those things together we're
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left with a 1 positive which gives us
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our sodium ion okay so the question that
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should be sort of obvious in your mind
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then is hey what happened to that one
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electron then well here's what happened
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metals give up their electrons nonmetals
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are going to gain electrons so that one
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electron that we lost what if we took
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that one electron that we lost from that
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sodium and we came over here and we put
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it on that fluorine that fluorine now
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went from having 7 to having 8 good what
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happened to the electron configuration
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well that electron configuration now is
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1s that doesn't change but the valence
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the twos here we had 2 in the s and we
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had five in the P but we added another
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one so now we have two p6 which you may
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note does a couple of things first off 2
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plus 6 is 8 that's 8 valence electrons
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we've satisfied the octet rule and that
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is the exact same electron configuration
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as we had for neon that is the noble gas
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electron configuration that's what we're
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looking for by the way that means that
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fluorine is no longer fluorine it is
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fluoride okay that anions we actually
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change the name of them at the end they
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become IDE at the end we'll get a little
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bit more into that when we talk about
00:15:05
naming later on that is now a fluoride
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ion if we put those two things together
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we would get a sodium fluoride sodium
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fluoride is the stuff that's in your
00:15:16
toothpaste um to prevent tooth decay
00:15:18
it's also why shouldn't swallow it
00:15:20
though because sodium fluoride is
00:15:21
poisonous it certainly in very large
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doses so don't eat your toothpaste spit
00:15:26
it out okay so sodium fluoride there so
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we got to a noble gas electron
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configuration we've
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two ions here the other thing that you
00:15:33
need to know is that they have names not
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just the ions themselves those obviously
00:15:37
have names fluoride and sodium you don't
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change the name of a metal you could
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just say that it is a sodium ion as long
00:15:44
as that thing only forms one type of ion
00:15:46
which we'll talk of a little bit about
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later but everything the first two
00:15:50
columns they only form one type of ion
00:15:52
it's this d-block stuff here that forms
00:15:54
other weirdness
00:15:55
okay what about the d-block stuff what
00:15:57
if we did that well if you wrote
00:15:59
electron configuration for anything in
00:16:01
the d-block okay you would still see
00:16:04
that your highest energy levels are
00:16:05
still going to be your s and your p
00:16:08
because remember the DS are always one
00:16:10
level below so this is level four here
00:16:12
right so this is 4s 4p but this is 3d so
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even if you went all the way over to
00:16:18
here then and you had all these D
00:16:21
electrons your highest energy level is
00:16:22
still going to be your 4s there and so
00:16:24
it's still only the s and P electrons
00:16:26
that are going to determine valence um
00:16:28
the last thing I want to make sure that
00:16:30
you know here in this video is that
00:16:32
things with positive charges have a
00:16:34
specific name they're called cations
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things with negative charges have a
00:16:39
specific name they're called anions and
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it's really important to me that you
00:16:43
actually call them properly their
00:16:45
cations and anions they're not cash ins
00:16:48
and anyons even though it sort of looks
00:16:49
that way on pronunciation wise so
00:16:52
cations anions cat means positive and
00:16:55
means negative you'll see a little bit
00:16:57
more of that if you take some
00:16:58
higher-level science classes you start
00:16:59
talking about positive and negative
00:17:00
cathodes and anodes and stuff like that
00:17:03
that by the way cathode cat cation
00:17:06
that's where some of that stuff is going
00:17:08
to come from so just keep that in mind
00:17:10
cathode means positive anion means
00:17:13
negative and that's the essential basics
00:17:16
of how we find valence electrons and how
00:17:18
we use them how we can look at that to
00:17:21
be able to form ions because we're
00:17:23
looking for a noble gas electron
00:17:24
configuration all right thanks kiddos
