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hello it's medicosa's perfect genetics
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where medicine makes perfect sense let's
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continue our general chemistry quick
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review playlist a playlist for busy
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people where we get straight to the
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point the last video was about the
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periodic table today we'll talk about
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the periodic trends the patterns of
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change in the periodic table namely the
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atomic radius the ionization energy
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electron affinity electronegativity and
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even metallic character for instance
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let's talk about the atomic radius as
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you go down a group the atomic radius
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keeps getting bigger and bigger and
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bigger you go from this to this because
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this one had only one shell but look
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here we have seven electron shells so
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the trend is that the atomic radius
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increases down a group and since it's a
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trend in the periodic table it's called
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periodic trend please watch the videos
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in this chemistry quick review playlist
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in order hit the like button if you
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remember my Ten Commandments of
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chemistry many of them included matter
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and energy as well as the implications
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of the periodic table matter could be
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Pure or could be a mixture pure matter
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could be an element or a compound today
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we're talking about the trends of the
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periodic table of the elements what's an
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element it's the simplest form of a
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substance which is physical matter an
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element is made of atoms for example
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oxygen element is made of oxygen atoms
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here is a very simplistic view of the
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atom in the center we have the nucleus
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around the nucleus we have shells that
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contain electrons are these shells well
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demarcated like drawn with a pencil no
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they are very vague poorly demarcated
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you can call them an electron cloud hazy
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blurry vague unclear the nucleus is
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positive why because it has neutrons
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which have no charge and protons which
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have positive charge so overall the
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nucleus is positive and around it we
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have a nucleus which is negative the
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positive and the negative cancel each
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other out and you end up with a neutral
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atom neutrons are neutral and located in
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the nucleus protons are positive also in
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the nucleus electrons are negative
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around the nucleus the neutrons are
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neutral protons are positive proton
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positive electrons negative let's talk
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about the masses the electron mass is so
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tiny it's almost insignificant you can
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ignore it here is the atomic mass and
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here's the atomic number the atomic
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number is the number of protons it's
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also the number of electrons the atomic
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mass or the mass number roughly speaking
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is the number of protons plus the number
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of neutrons why isn't it a whole number
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because it's a weighted average as we
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have discussed before number of protons
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equal the number of electrons and this
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is called hold the atomic number since
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the positive charges equal the negative
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charges you have a neutral atom but what
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if the number of protons exceed the
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number of electrons then you have a
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positive ion what if the number of the
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negative electrons exceed the number of
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positive protons then you have a
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negative ion what if the number of
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protons equal the number of electrons
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but the number of neutrons is different
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that's an isotope such as carbon 13
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carbon 14
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Etc in the last video we talked about
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the periodic table don't forget we go
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horizontally we call them periods or
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rows or a series of elements number one
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has one energy shell how about period
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number two well each element has two
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shells of electrons in Period three you
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have three shells of electrons I said
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shell not subshell how about period
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number seven it has seven shells of
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electrons next let's go vertically now
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we call this a group or a family of
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element Group 1 has one electron in the
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outermost shell called the valence shell
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group 2 has two electrons group 3A or
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thirteen three electrons Group 17 or 7A
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seven electrons in the outermost shell
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group 18 the noble gases eight electron
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in the outermost shell if you have eight
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electrons in your outermost shell you
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are called stable and this is the octet
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rule octet means eight now let's talk
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about the periodic trends first atomic
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radius definition atomic radius the
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radius of the atom thank you Captain
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genius and of course the radius is half
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the diameter so the radius is from the
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center to the outermost part I.E it's
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the distance between the nucleus of the
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atom and the edge of the atom as the
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edge of the atom clearly demarcated as
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if it was drawn by a sharp pencil heck
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no it is vague we're uncertain about the
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edge of the atom it is not clearly
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demarcated therefore there is a better
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definition here's an atom here's another
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atom take the distance between this
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nucleus and this nucleus and give me
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half of that distance and that will be
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the radius of the atom this definition
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is more accurate than this definition
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let's talk about the atomic radius Trend
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down a group and across a period first
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down a group think about it we went from
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one electron shell into seven electron
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shell so of course this atom is way
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bigger than this atom the atomic radius
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here is bigger than the atomic radius
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here makes perfect sense so as I go down
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a group my atomic radius keeps getting
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bigger and bigger and bigger we're done
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with down a group now let's talk about
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the atomic radius Trend across a period
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as I go from here to here what do you
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think is going to happen why well let's
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see I went from three protons and three
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electrons to four protons four electrons
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five protons five electrons six protons
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etc etc so as I go from the left to the
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right the number of positive protons go
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up and the number of negative electrons
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go up and as you know Opposites Attract
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which means on the left the attraction
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between the positive and the negative is
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weak but as you go to the right because
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you're adding more protons and more
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electrons you're adding more positive
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charges and more negative charges you're
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adding more attraction forces which
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means the atom will get smaller and
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smaller and smaller because of the
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positive nucleus is attracting the
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negative electrons more and more and
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more so you shrink and shrink and Shrink
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so as you go across a period the atomic
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radius decreases so atomic radius down a
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group it goes up across a period it goes
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down next ionization energy what the
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flip is that think about it it's called
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Energy ionization what's an ion oh an
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ion is something that's not neutral
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exactly here we're trying to remove a
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negative electron when you remove a
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negative electron the atom becomes a
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positive ion I.E A cation so think of
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ionization energy as the energy needed
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to make a positive ion it's the energy
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needed to remove an electron from a
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neutral atom in the gaseous State now
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let's think about the trend let's start
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on the upper left part of the periodic
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table the atom is small which means the
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outermost electron is close to the
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nucleus yes which means the positive
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charge and the negative charge are
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attracting each other which means it's
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very difficult to get that electron on
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out of the atom because it's close
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enough to the positive nucleus
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conversely as you go down down down down
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down down down a group look what
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happened here the further most electron
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is here which is far away from the
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positive nucleus which means it's easier
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to remove that electron compared to that
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electron I.E by going down a group here
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ionization energy decreases the energy
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needed to remove an electron gets lower
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and lower and lower because it gets
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easier to move an electron the farther
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it gets from the nucleus and that was
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the trend of ionization energy down a
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group how about across a period think
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about it across a period the electron
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keeps getting closer and closer and
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closer and closer to the nucleus which
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means it gets harder to remove that
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electron from the atom I.E it takes more
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energy which means ionization energy
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goes up next electron affinity has the
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opposite definition of ionization energy
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ionization energy was trying to remove
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an electron away from the atom but look
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here at electron affinity this is how
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easily an atom attracts and accepts an
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electron go away versus come closer so
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the definition is the opposite however
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the trend is the same down a group
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electron affinity decreases across a
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period it increases just like ionization
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energy but I don't get it let's think
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about it Affinity means love which two
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people love one another the most those
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who are very close to each other I.E a
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positive nucleus and a negative electron
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or those who are far away from one
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another of course these two love each
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other more perfect so the electron
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affinity here is high as you go down
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electron affinity decreases oh that
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makes sense moreover when you go across
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a period you keep adding more positive
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charges and more negative charges so
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they attract to one another more they
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tend to love each other more on the
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right side than on the left side so
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across a period electron affinity
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increases the fourth concept is
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electronegativity as you know electrons
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are negative I want you to look at your
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periodic table let's look at sodium for
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example which is number 11. I want you
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also to look at chlorine which is number
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17. they are in the same Row in the same
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period correct yes they are which one
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has more positive charges I.E protons
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answer chlorine of course the one on the
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right side chlorine has more protons
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than sodium okay let's talk about
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electrons which one has more electrons
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is it sodium or chlorine answer also
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chlorine nice how many electrons does
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sodium have in the outermost shell the
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answer is one I said shell not sub shell
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the configuration of sodium is 2 8 1 2
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electrons in the first shell eight in
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the second shell one in the third shell
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how about chlorine chlorine has 17 so
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the configuration is 2 8 7 and to
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achieve stability I.E the octet sodium
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would love to lose an electron but
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chlorine the one on the right side would
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love to gain another electron to become
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octet to become like the noble gas argon
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which means chlorine has more ability to
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attract an electron therefore higher
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electronegativity so across a period
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electronegativity increases let me make
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it easier for you who's the most
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electronegative answer fluorine so if
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you're getting closer to fluorine
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electronegativity goes up look at this
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I'm going to the right oh and fluorine
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is on the right exactly if you're going
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towards fluorine if you're going to the
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most electronegative therefore
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electronegativity will increase across a
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period if you go up a group you're
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getting closer to fluorine so
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electronegativity increases but if
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you're going down a group away from
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fluorine away from the most
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electronegative therefore
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electronegativity decreases on average
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smaller atoms are more electronegative
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than large atoms which makes sense
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because if you're small it means there
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is less electron shielding I.E less
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electrons are covering around the
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nucleus so it is easier for you to
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attract an electron from the outside
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world last metallic character was that
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it's the quantum level reactivity of a
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metal and as you know reactivity of the
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metal is based on the tendency to lose
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electrons which is the opposite of
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electronegativity because
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electronegativity was about attracting
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an electron but metallic characters
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about losing an electron and since
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electronegativity went up as I go up and
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to the right therefore metallic
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character has to be the opposite it
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increases as I go down and to the left
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see chemistry makes so much sense once
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you understand what the flip you're
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talking about so let's summarize atomic
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radius down a group it increases across
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a period it decreases if you want
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ionization energy it's the opposite down
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a group goes down across a period goes
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up then electron affinity is the same
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Trend
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electronegativity almost the same Trend
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just remember fluorine is the most
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electronegative how about metallic
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character the exact opposite of
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electronegativity electronegative
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activity goes up if you go to the right
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and upwards metallic character goes up
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if you're going to the left and
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downwards so let's draw all of this on
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the periodic table first atomic radius
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if you're going downstairs it increases
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conversely ionization energy electron
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affinity and electronegativity decrease
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as you go down let's go across a period
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atomic radius decreases however
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ionization energy and electron affinity
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and electronegativity go up how about
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metallic character it's the opposite of
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electronegativity who is the most
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electronegative fluorine which means as
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you go to the right and upwards
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electronegativity goes up metallic
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character is the opposite as you go down
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and to the left metallic character
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increases that's it it's easy peasy you
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can download my handwritten notes on my
00:14:58
website medicosis perfect nellis.com
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let's answer the question of the
00:15:02
previous video how many electrons does
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carbon have in its valence shell I'm
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talking of course about a neutral atom
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please pause and try to answer this
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yourself okay here is carbon what's the
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atomic number of carbon 6 which means
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how many electrons does carbon have in
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total answer six configuration based on
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shells not subshells just shells two
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okay how many are left four so that the
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total is six so the first shell has two
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and then the outer shell or the valence
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shell has four so the answer here is
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four if you have one or two or three
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electron in the outermost shell you tend
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to lose them to become a positive ion
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but if you have a five six or seven
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electron on the outermost shell you will
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tend to gain more electrons to become a
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negative ion but what if you're stuck in
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the middle what if you have four
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electron in the outermost shell then you
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will neither lose nor gain instead you
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will share electrons I.E covalent bond
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and you will see carbon with four bonds
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with hydrogen so that we are sharing
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four electrons so now carbon has
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achieved the octet rule and what's that
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hydrocarbon and you'll see this all over
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organic chemistry question of the day if
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electronegativity of sodium is 0.93 and
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electronegativity of chlorine is 3.16
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let me pause for a second and tell you
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that the electronegativity of chlorine
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is greater than that of sodium which
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makes sense because chlorine is more to
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the right chlorine is closer to fluorine
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which is the most electronegative that's
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why chlorine is more electronegative
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anyway if the electronegativity of
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sodium is this and chlorine is this then
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the type of bond in sodium chloride is
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nonpolar covalent polar covalent ionic
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or metallic let me know your answer in
00:17:09
the comments you'll find the answer key
00:17:11
in the next video you do not want to
00:17:13
miss the next video because we'll have
00:17:15
more questions are you struggling with
00:17:18
kidney physiology the glomerular
00:17:20
filtration rate the proximal tubule the
00:17:22
loop of Henley the distal tibial the
00:17:24
counter current multiplier the
00:17:26
titratable acidity of the collecting
00:17:29
ducts you can Master these Topics by
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downloading my renal physiology course
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on my website
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study hard this is medicosa's
00:18:02
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00:18:04
perfect sense
