OK ladies and gentlemen - time for anohter exciting
episode of rocks and minerals this one
is about mineral classification if you
remember in previous episodes we talked
about the elements and looked at the
periodic table
And remember their's 118 elements in the
periodic table but only 92 elements are
naturally occurring the rest are all
synthetic made in a laboratory but if we
look further it turns out that we're
talking about the Earth's crust only about
eight elements make up most
of the Earth's crust
about 98.9% of the Earth's crust
is eight elements and those are oxygen
which is almost 50 percent silicon over
a quarter then aluminum iron calcium
sodium magnesium potassium and all the
rest make up only about one percent or
so and it turns out that you only need a
few elements to make up most of the Earth's crust
but they actually can combine to form
compounds in many many different ways
it's thousands of different compounds so it
turns out most minerals are compounds so
and they're driven by the outer valence
electrons so turns out all the atoms
want a full shell so if you look at the
periodic table here if you look at the
far right there the last column column
18 or 8A Helium Neon Argon Krypton
Xenon they don't have full shells in the
outer shell in their valence electron
shell and that's what all the elements
want to be but only the Noble Gases
I'll just show you an
example here Helium you notice Helium
has two electrons in its shell so it's
perfectly happily the way it is the next one
here is Neon
you notice Neon is 2, 8 so that's 2
in the first shell 8 in the second shell so
it's perfectly happy the way it is it
does not to react with anything next one
here Argon
it has three shells but you notice it also has
eight electrons in its outer shell so
it's all full shells and they're
perfectly happy the way they are now if
you contrast this with by the way they
call us the Octet Rule that all the
atoms want to have eight electrons in
its outer shell but it turns out if you
look at some of these elements
let's go down to periodic table here
like in the far left for example like
number 11 Atomic Number 11 sodium
or number 19 potassium there's a sodium noticesodium only has one electron in its
outer shell so it wants to have either
it needs to either gain seven electrons or
lose one electron well obviously it's easier to lose one electron so it's gonna go
and it's gonna get rid of one electron
it's called donating an electron and
it's gonna become a positive ion
called a cation and another example here
is gonna be potassium
is very similar it's right below in
the periodic table it also has one
electron that it's gonna donate and become
a positive potassium ion which they
call it cation if we go to the other side
of the periodic table you'll see like
column 7a or 17 you have fluorine
chlorine bromine iodine astatine  let's look at
some of those here here's fluorine you
notice fluorine has two electrons in its inner shell
and then seven electrons so it needs to
add one electron to to meet the octet
rule and chlorine is right below it in
the periodic table and it's exactly the
same it has seven electrons and what it's gonna do is try to get one more electron to
make the octet rule work so what
happens is these atoms will form bonds
with other atoms and it turns out that
is actually three different ways that
can form bonds 
there's three kinds of bonds there's Ionic
bonds there's Covalent bonds and then
there's Metallic bonds but we'll
talk about each one these here
so what happens with Ionic Bonds
ions of opposite sign attract each
other so for instance we talked about
before how sodium what it'll do is get
rid of one of the electrons become a
cation and then chlorine will add one electron and
become a anion and what they'll do is
this is the ionic bond they will
bond to each other positive
negatives attract  the sodium
donates one electron the chlorine
picks up the electron and they're now
happy and of course we know this is
sodium chloride and the exact same thing
happens with potassium you look at
potassium potassium will do
the exact same thing get rid of the
electron and it'll combine with the
chlorine also and you also end up
getting potassium chloride
which by the way is a mineral
called Sylvite the Sodium Chloride is a
mineral called halite which we know as
salt and potassium chloride is sylvite
now these are all part of the halide
group so we're getting back to how we
categorize these things and so that's
the halide group that's because they are
using the anion is from the halogens fluorine chlorine
bromine iodine so anyway the next the
next bond we're gonna talk about here is
the a covalent bond and this is
where atoms share electrons and let me
just give you a couple examples of
covalent bonds if you go back to our
hydrogen atom here you notice it's got
one electron and it's a neutral atom but
it wants to have two electrons of none two hydrogen atoms and they'll actually will
share their two electrons and as far as
the atoms are concerned the nucleus of the
hydrogen atoms think that there is two
electrons they both think that they have
two electrons and they're perfectly happy
with what they have
that's a covalent bond
I'll give you one more example a
covalent bond  if you take
the hydrogen that has one electron
and if you take Carbon let's take a look
at carbon on the periodic table you notice
carbon is on Group 4A and
it's atomic number six so carbon has if we
look at the electron configuration it
has two electrons in the inner shell
and the outer shell has four electrons
well how does it get to eight we could
either gain four or lose four electrons to
get the right number
this periodic table here
shows the oxidation states
and there's a lot of choices it can have
but it can either have a become a plus
four ion or minus four ion or some other
choices as well carbon will combine with
hydrogen take the one carbon
which has four electrons in its outer
shell and the hydrogens are come along
have one electron in its outer shell and
carbon will share  electrons
with four hydrogen atoms and that's a gas called methane and
that's CH4 and that's a perfectly good
arrangement here and by the way when it
finally forms these things you know it's
just like and on two dimensions we drew
these things you know the H is on the
top and then one's on the bottom one's
on the left one's one the right they try to be
as far apart from each other as possible
well in three dimensions the ideal
arrangement is actually a tetrahedron
it's called a tetrahedron shape but you
notice it's got the carbon is in the
middle and then the hydrogens are
around it in kind of a pyramid shape
and what they're trying to do is be as
far away from each other as possible and
that's the tetrahedron of the methane
and by the way
methane is an organic compound
because it has carbon in it so if you
see something with carbon hydrogen and oxygen in it they're organic compounds and there's a
whole science of organic chemistry in
fact it's the basis for life on Earth
at least the kind of life that we know
like mammals and
reptiles and plants is carbon-based I'll
do one more example of a covalent bond
here and I'll use silicon here now
again we look on the periodic table
look at this one again this one shows
the oxidation states and notice Atomic
Number 14 it's right below carbon so it
has this almost the same electron
configuration in the outer shell so I
could find that where is silicon here's
silicon right you notice again it has
four electrons in the outer shell so I
can do something very similar to carbon
is form these compounds so turns out if
I take a look at let's take a look at
oxygen here let's look on a periodic
table first on the periodic table
oxygen is Group 6A right so
it's basically two groups away
from being Neon so if I look at the
oxygen electron configuration it's got
six electrons in the outer shell so it
wants to do is add two electrons now if
it does that it's gonna have a minus 2
charge so now if I take the silicon
which has four electrons I can actually
hook up silicon this way you see the
silicon will begin a middle and they'll
have four oxygens around it and again
each oxygens is -2 charge
right because there's two extra electrons
so times four oxygens is -8
and the silicon will be plus four it'll
get rid of the four electrons and then
we have everybody's happy there and then
it turns out it's very similar to the
methane by the way
this is called Silica this here it's
an ion a Silica ion here and this
will have covalent bonds and you'll see
how the Silica in the middle has eight
electrons so it thinks it has a perfect
octet but also the oxygens have the same
thing they look like they're also
surrounded by eight electrons
and turns out they also will form a
tetrahedron shape with the silicon in
the middle and the oxygens at the
corners of the pyramid so there's our
tetrahedron structure for the Silica
so that's the different kind of
bonds the last bond we have and it's
called a metallic bond and this one's
kind of hard to understand basically
what happens is for metals
let's just take a look at one of the
metals here's copper it's in
column 11 it's a group 11 Atomic Number 29 and copper's electron
configuration see it's got three full
shells and then the last shell has
one electron in that shell
so what copper's gonna do is form a crystal with other
copper atoms it's gonna get rid of that
electron kick it out and it'll form
a Lattice structure with all it with
another copper atom just like it and a
whole bunch of other copper atoms and
meanwhile the electrons will be kind of
just like flowing around them and
they're kind of shared by you all and
the end up what they call a sea of
electrons so you have all these copper ions
and they're all plus-one and they are
all surrounded by a sea of electrons and
the electrons are kind of shared by
all the atoms all the copper ions and
by the way this is why
copper is such a good conductor if you
put electric fields across this all the
electrons will start to drift in one
direction and you get a current flowing
so anyway it turns out that you know go
back to copper here it's got one
electron if you go down below it in the
periodic table is silver number 47
and below that is gold number 79 so if you
see here they have almost the same
electron configuration they're larger
but they all have one electron
in the outer shell there's silver and
there's gold
so they do exactly the same thing and
that's why silver gold and copper they
all act very similarly to one
another now talk about one other thing
here is we talked about these oxidation
states  oxidation states
so we talked about oxygen having six
valence electrons you know it wants to gain
two electrons to become an oxygen -2
ion
And meanwhile hydrogen has one electron and it wants to get rid of that to become a
hydrogen plus ion well it turns out if
you're if those two things met up
somewhere they would actually form a
it's kind of like a compound and be an OH
and they get together but these things
aren't complete in itself so there you
see an upper left there the oxide ion
the Oxygen -2 has eight electrons
and on the bottom in the middle you have
the hydrogen ion H+ got no electrons
well it could connect with a covalent
bond to form a
hydroxide ion so an OH and you notice
since it's got a minus 2 for
the oxygen ion and plus one for the
hydrogen ion they'll have a minus 1
charge and this is called a hydroxide
ion and now it turns out suppose you had
one of these hydroxide ions just
floating around and let's take a look at
aluminum here on a periodic table
aluminum is atomic number 13 and
let's take a look at aluminum's
electron configuration and you notice it has
3 electrons in the outer shell so it really
wants to do better than
that so it turns out that what
happens is aluminum could actually
bond with this hydroxide ion and it'll do
it with three of them and aluminum will be
perfectly happy it'll be
aluminum with three hydroxides
and by the way this is called Aluminum
Hydroxide and it's also the mineral
gibbsite which is in the hydroxide group so we're back
to how do we categorize minerals so
that's the hydroxides let's get to the
next the next slide here is how do we
categorize these minerals so minerals
are classified there's over 4,000 known
minerals and we need a way to classify and
organize them so they're classified by
a chemical composition into groups and
Now I put them into these twelve Groups here I got this from my book that I've
reviewed and I don't think there's any
standard order for putting these into a
particular order but I ended up with these
twelve here and I just label them here
picture here it's Native Elements Sulfides Sulfosalts Oxides
Hydroxides Halides number seven I've got
Carbonates then Phosphates Chromates
Titanates and Molybdates then Borates and Nitrates then Sulfates then Silicates and
finally the last one is Mineraloids which
actually aren't minerals so that's the
way we classify minerals and now it turns
out that some of the groups are very
large groups and they are further subdivided by either the element or crystal structure
into subgroups so this is what basically
where I'm going to end right now and
this is a first part of Mineral Classification.
