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8/6/2019 03 Minerals Chapter 3
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The Atom
Minerals are made up of atoms, and atoms are composed of three subatomic particles: the proton,
neutron, and electron. The protons and neutrons make up the nucleus of the atom. Electrons orbit
the nucleus in distinct shells. What makes one atom different from another atom is the number of
protons (e.g. all carbon atoms have 6 protons whereas all nitrogen atoms have 7). All atoms are
electrically neutralbecause they have the same number of electrons (with a negative charge) orbiting
the nucleus as they have protons (with apositive charge) inside the nucleus. The opposite chargescancel each other out.
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Figure 3.4BThe Atom in 3-D
Remember, there are
the same number ofelectrons orbiting the
nucleus as there are
protons in the
nucleus. However,
each electron shellcan only hold a
certain number of
electrons, and the
electrons fill the shell
closest to the nucleus
first, and then build
out.(Can only hold 2 electrons)
(Can hold 18 electrons)
(Can hold 8 electrons)
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This shell
can hold 18.
For the 3rd (and higher
shells), once the shell
gets 8 electrons, the next
2 electrons picked up will
go to the next shell out(see below). Additional
electrons will then fill in
the lower (incomplete)
shell as needed.
This shell
can hold 8.
This shell
can hold 2.
An elementis made up of only one type of
atom. The atomic numberof an element is
the number ofprotons in the nucleus.
Noticethe
number
of
protons
and
electrons
is always
equal.
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Figure 3.3The Periodic Table
All elements in theAcolumns have the same number of electrons in their outer shell.
(e.g. 1A elements all have one electron in their outer shell, and 6A elements all have 6
electrons in their outer shell).
All elements on the same rowhave the same number of electron shells.
Note everything to the left of this stair-stepped
line is a metal.
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All other elements desire to have 8 electrons in their outer shell. This is the Octet
Rule. To achieve this electron configuration like the noble gases, atoms may lose,
gain, or share electrons to have 8 in their outermost shell (see details on previoustwo slides). Metals (since they generally only have 1 or 2 electrons in their outer
shell) tend to lose those outer electrons so that shell is no more. The remaining
lower shell has 8. Nonmetals that have 6 or 7 electrons in the outer shell tend to
gain 1 or 2 more to get to 8. Two nonmetals (both wanting 1 or 2 more electrons)
tend to share electrons to get to 8 (again, see details on previous slide).
When atoms lose or gain electrons they are no longer electrically neutral. Atoms
that have lost or gained electrons are now electrically-charged particles and are
called ions. Atoms that lose the negatively-charged electrons have a net positivecharge and are called cations. Atoms that gain electrons have a net negative
charge and are called anions.
Only the Noble gases (far right column on the periodic table) are content with their
present electron configuration. (except for Helium which has a full shell with 2
electrons, all other noble gases have 8 electrons in their outer shell).
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Testing 1, 2, 3 (click mouse for answers)1) What is a naturally occurring, inorganic, crystalline solid?
a. Atom b. Ion c. Mineral
2) Minerals are made of atoms. What are atoms made of?
a. Protons b. Neutrons c. Electrons d. All the above
3) Which element has 14 protons in its nucleus?
a. Carbon b. Sodium c. Silicon
4) How many electrons can the first energy shell hold?
a. 2 b. 4 c. 8
5) A substance comprised of only one type of atom is called a(n):
a. Atom b. compound c. element
6) According to the Octet Rule most atoms desire to have _____ electrons orbiting in its outer
shell.
a. 4 b. 8 c. 18
7) Are metals electron gainers or losers? a. Gainers b. Losers
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Figure 3.5
IONIC BONDING occurs between ions with opposite electrical charges.
Generally ionic bonding occurs between metals (electron losers) and nonmetals
(electron gainers).
1) This single electron in the
3rd shell of sodium is
stripped off and added to
the 7 other electrons in theouter shell of chlorine. This
gives both atoms 8
electrons in their outer
shells.
2a) This shell
disappears
because
there are no
electrons
there. Notethe new
outer shell
has 8.
2b)
Chlorine
now has 8
electrons
in its
outershell.
3a) This sodium
ion has 11
protons (+) and
only 10 electrons(-) leaving it with
a +1 ionic charge.
3b) This chlorine
ion has 17
protons (+) and
18 electrons (-)leaving it with a -
1 ionic charge.
4) Since sodium has a + charge, and chlorine
has a charge, they are attracted to eachother producing the ionic bond.
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Figure 3.6
The mineral halite (table salt) occurs from the ionic bonding
between chlorine and sodium. The fact that salt dissolves inwater is evidence that an ionic bond is not very strong.
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Figure 3.9
The
chemical
formula forhalite is
NaCl. There
are an
equal
number of
sodium and
chlorine
atoms in
halite (a
one to one
ratio).
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Figure 3.7
COVALENT BONDINGgenerally occurs between
two nonmetalsIll share one of
my electrons withyou if you will
share one of
yours with me!
Why, sure! I
would love
that!
Here, each chlorine atom shares one of its outer electrons with the other
so that both have 8 electrons orbiting around them (although those twoshared electrons spend their time orbiting around both).
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Figure 3.10ACovalent bonds
The carbon atoms
in diamond all sharetheir 4 outer
electrons with 4
surrounding carbon
atoms. The
electrons are
shared equallymaking the bond
very strong. This
explains why
diamond is the
hardest naturalmineral on earth.
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Know who this Diamond is?
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Cleavage (a splitting property of some minerals) is the result of weaker bond
strengths along different planes within a mineral.
Most chemical bonds are partially ionic and partially covalent [the electrons are
shared, but not equally (they spend more time around one atom than the
other)]. The more covalent they are, the stronger they are. The more ionic they
are, the weaker they are.
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METALLIC BONDING
Metallic bonding occurs when metal atoms get so close their outer electrons
circle a group of atoms bonding them together. This is relatively rare in
nature, and only four metals (gold, silver, copper, and platinum) occur as
true minerals.
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One additional type of chemical bond is called
a van der Waal bond. This is a very weak bond
between residual charges. There is no sharing
or trading of electrons. Van der Waal bondshold the sheets of graphite together. Graphite
is used as pencil lead. The bonds are so weak
that when graphite slides across a piece of
paper the sheets are stripped off leaving the
pencil mark behind.
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The arrangement of atoms is determined by their
electrical charge (opposite charges like to be near each
other), and their relative sizes [note how sodium (Na)
ions fits nicely into the pockets created by the
arrangement of the chlorine (Cl) ions].
Do you know what this is?
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Testing 1, 2, 3 (click mouse for answers)8. The chemical bond that occurs between positively and negatively-charged ions is called a(n):
a. ionic b. covalent c. metallic
9. What is the bond called where atoms share outer electrons?
ionic b. covalent c. metallic
10. Which bond below is the strongest?
a. ionic b. covalent c. metallic
11. Give an example of a mineral formed from ionic bonding.
diamond b. gold c. halite
12. Give an example of a mineral formed from covalent bonding.
a. diamond b. gold c. halite
13. What metal below occurs naturally in nature?
iron b. zinc c. copper
14. Minerals that tend to splitalong planes of weakness due to weaker bonds along that plane have:
a. fracture. b. planity. c. cleavage. 6/7/2011
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The 8 most abundant elements in earths crust are:
These 8 elements make up
99.2% of all the Earths crust.
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Here we see both the ionic charge and relative sizes of the 8 most abundant
elements. Both charge and size determines how the atoms will arrange
together to form minerals.
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Figure 3.19
silicon-
oxygen
tetrahedron
This silicon-oxygen
tetrahedron is the
building block for 92%
of all minerals in the
earths crust. It has a -4
ionic charge. All
minerals composed of
this radicalorpolyatomic ion are
called silicates.
+4
-2
-2
-2
-2
Overall -4
charge
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Figure 3.23
Silicate minerals
are groupedbased upon the
structural
configuration of
the
tetrahedrons,
and/or theirchemical
composition.
These are all
silicates
Only 8% of all minerals in
earths crust are
nonsilicates.
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The silicate minerals
can be grouped by thestructuralarrangement
of tetrahedrons into
one of the 5 groups as
shown. The
tetrahedrons may be
isolated (singletetrahedron), or they
may share oxygens to
make up the other four
groups.
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Figure 3.22A
Here are some mineral groups associated with these silicate structures.
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Here are some more mineral groups associated with these silicate structures.
Feldspars
are 3-D
silicates in
which
some of
the silicon
sites areoccupied
by
aluminum.
Quartz is the
only
common
mineral
comprised
solely of
silicon and
oxygen.
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Silicate minerals can also be grouped by their chemical composition. For
example, do they contain iron or magnesium in their chemical makeup? If
they do they are calledferromagnesian silicates. If not, they are called
nonferromagnesiansilicates.
Nonferromagnesian
silicates are generally
light-colored.
Ferromagnesian silicates
are generally dark-
colored.quartz
biotite mica
hornblende
feldspars
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Figure 3.11B
Quartz crystals showing striations.
Quartz is a nonferromagnesian silicates
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Figure 3.16
Quartz showing
conchoidal
fracturing.
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Figure 3.24Potassium Feldspar: (a nonferromagnesian
silicate) showing cleavage plane on top and
front of specimen.
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Figure 3.25
Plagioclase feldspar (a nonferromagnesian
silicate) showing color playand striations
(the parallel lines) on a cleavage face.
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Testing 1, 2, 3 (click mouse for answers)
15. What are the 2 most abundant elements in Earths crust?
a. silicon and iron b. iron and aluminum c. silicon and oxygen
16. What is the shape formed by the joining together of four oxygen atoms around one silicon atom?
a. octahedron b. tetrahedron c. dodecahedron
17. What do tetrahedrons share to join together?
a. silicon atoms b. aluminum atoms c. oxygen atoms
18. Give an example of a mineral formed solely from oxygen and silicon.
a. quartz b. feldspar c. mica
19. What element do all feldspars have that is not contained in quartz?a. aluminum b. oxygen c. silicon
20. Ferromagnesian silicates all contain iron or magnesium and are typically ______ in color.
a. light b. dark
6/7/2011
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Nonsilicate minerals are grouped by their chemical composition.
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Graphite and diamond are not only native elements, they are also
polymorphs (same composition, different arrangement of the atoms) of
carbon. Both are pure (100%) carbon.
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Figure 3.11A
Pyrite (FeS2), also known as Fools Gold, is a sulfide.
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Precious stones
are beautiful,
durable, and
rare.
Semiprecious
stones lack at
least one of the
three qualities
above. (generallythey are not that
rare).
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Testing 1, 2, 3 (click mouse for answers)
21. All carbonate minerals would have what radical in their chemical formula?
a. SO4 b. CO3 c. SiO4
22. Give an example of a carbonate mineral.
a. quartz b. halite c. calcite
23. What radical would you find in all sulfate minerals?
a. SO4 b. CO3 c. SiO4
24. Which mineral below is not a native element?
a. gold b. copper c. lead
25. Which gem below is semiprecious?
a. daimond b. garnet c. emerald
6/7/2011
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and guys, some minerals can make
your life much more
enjoyable!