03 Minerals Chapter 3

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

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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!

03 Minerals Chapter 3

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