The Atom

The Atomic Theory:

In 1911, Rutherford proposed a revolutionary view of the atom. He suggested that the atom consisted of a small, dense core of positively charged particles in the center (or nucleus) of the atom, surrounded by a swirling ring of electrons. The nucleus was so dense that the alpha particles would bounce off of it, but the electrons were so tiny, and spread out at such great distances, that the alpha particles would pass right through this area of the atom. Rutherford's atom resembled a tiny solar system with the positively charged nucleus always at the center and the electrons revolving around the nucleus.

Interpreting Rutherford's Gold Foil Experiment: The positively charged particles in the nucleus of the atom were called protons.  Protons carry an equal, but opposite, charge to electrons, but protons are much larger and heavier than electrons.  

In 1932, James Chadwick discovered a third type of subatomic particle, which he named the neutron. Neutrons help stabilize the protons in the atom's nucleus. Because the nucleus is so tightly packed together, the positively charged protons would tend to repel each other normally. Neutrons help to reduce the repulsion between protons and stabilize the atom's nucleus. Neutrons always reside in the nucleus of atoms and they are about the same size as protons. However, neutrons do not have any electrical charge; they are electrically neutral.

Atoms are electrically neutral because the number of protons (+ charges) is equal to the number of electrons (- charges) and thus the two cancel out.  As the atom gets larger, the number of protons increases, and so does the number of electrons (in the neutral state of the atom). 

Each element has its own distinct line spectra.  

To Bohr, the line spectra phenomenon showed that atoms could not emit energy continuously, but only in very precise quantities (he described the energy emitted as quantized). Because the emitted light was due to the movement of electrons, Bohr suggested that electrons could not move continuously in the atom (as Rutherford had suggested) but only in precise steps. Bohr hypothesized that electrons occupy specific energy levels. When an atom is excited, such as during heating, electrons can jump to higher levels. When the electrons fall back to lower energy levels, precise quanta of energy are released as specific wavelengths (lines) of light.

Under Bohr's theory, an electron's energy levels (also called electron shells) can be imagined as concentric circles around the nucleus. Normally, electrons exist in the ground state, meaning they occupy the lowest energy level possible (the electron shell closest to the nucleus). When an electron is excited by adding energy to an atom (for example, when it is heated), the electron will absorb energy, "jump" to a higher energy level, and spin in the higher energy level. After a short time, this electron will spontaneously "fall" back to a lower energy level, giving off a quantum of light energy. Key to Bohr's theory was the fact that the electron could only "jump" and "fall" to precise energy levels, thus emitting a limited spectrum of light.

Properties of elements repeat periodically. Similar elements form a group.

	I	II		III	IV	V	VI	VII	VIII
	H								He
	1								2
	Li	Be		B	C	N	O	F	Ne
	3	4		5	6	7	8	9	10
	Na	Mg		Al	Si	P	S	Cl	Ar
	11	12		13	14	15	16	17	18
	K	Ca		Ga	Ge	As	Se	Br	Kr
	19	20	Transition	31	32	33	34	35	36
	Rb	Sr	metals	In	Sn	Sb	Te	I	Xe
	37	38		49	50	51	52	53	54
	Cs	Ba		Tl	Pb	Bi	Po	At	Rn
	55	56		81	82	83	84	85	86

            Formation of compounds

All things are made up of tiny particles called atoms. Helium, neon, argon, krypton are inert gases. They have 2, 8, 8, and 8 electrons respectively in their outermost shell. If any atom gets eight electrons in the outer shell, it becomes stable. This is the octet rule.

Oxygen has six electrons in the outermost shell. They are called valence electrons. If however, there are eight electrons in its valence shell, it becomes stable. The electron affinity of oxygen is more. By losing electrons into the neighborhood or gaining electrons from the neighborhood, atoms become stable in form [compounds].

Sl no	Name	Symbol	configuration
1	Hydrogen	H	1
2	Carbon	C	2,    4
3	oxygen	O	2,    6
4	Sodium	Na	2,    8,   1
5	Chlorine	Cl	2,    8,   7

Atoms can share electrons to form molecules.

Example:- H2, O2, N2, CO2 [covalent bond formation]

            H─H,  O═O, N≡N,  O═C═O

Atoms can donate electrons to form molecules.[transfer of electrons]

Example:- NaCl , NaOH, CaCO₃, NH₄OH [ ionic bonds]

            Na⁺ Cl^-  , Na⁺ OH^-  ,  Ca²⁺CO₃^2-        NH4⁺ OH^-                

Sodium donated its outer shell electron to chlorine and both have now eight electrons in their outer shell and therefore they are stable.

The earth's atmosphere has N2, O2, CO2, and H2O molecules as gases.

Sea water is H2O with many dissolved compounds like NaCl, MgCl2, CaCl2, MgSO4 CaSO4 etc. Water is a polar molecule and a good solvent.

When oxides of non-metals dissolve into water, the water becomes acidic due to an excess of H+ ions in water. [Acid is formed]. The acids are more reactive.

When hydroxides dissolve in water, the water becomes basic due to an excess of OH- ions.

[Base is formed]. The bases are more reactive.

Therefore compounds can form by;

• Only covalent bonds.
• Only ionic bonds.
• By the combination of both, covalent and ionic bonds.

Chemistry is all about understanding the nature of atoms and the formation of bonds.

Enthalpy change:

While forming new bonds, energy is liberated. Therefore bond formation is exothermic.

(for Carbon to Carbon bond formation, energy is needed from an external source.)

Breaking bonds need energy. Therefore bond breaking is endothermic.

In a chemical change either energy is given out or energy is taken in. Energy is conserved.

Hydrogen and oxygen combine to form water. This is an exothermic reaction.

2H2(g) + O2(g) → 2H2O(l). two molecules of hydrogen gas combine with one molecule of oxygen to form two molecules of water.   

Oxidation and reduction:

Oxidation: - loss of electrons by any species is oxidation.

4Al (s) + 3O2 (g) → 2Al₂O₃ (s)

Aluminum is oxidized to Al2O3

Reduction: - a gain of electrons by any species is reduction.

            ZnO (s) + C (s) →Zn (s) + CO2 (g)

           

            Zinc oxide is reduced to Zn

The Earth's crust:

According to calculations by F. W. Clarke, a little more than 47 percent of Earth's crust consists of oxygen. It occurs mainly in the form of oxides, particularly silica, alumina, iron oxides, lime, magnesia, potash, and soda. Silica functions principally as an acid, forming silicates, and the most common minerals of igneous rocks are silicates. From a computation based on 1,672 analyses of all kinds of rocks, Clarke arrived at the following values for the average percentage composition: SiO₂=59.71; Al₂O₃=15.41; Fe₂O₃=2.63; FeO=3.52; MgO=4.36; CaO=4.90; Na₂O=3.55; K₂O=2.80; H₂O=1.52; TiO₂=0.60; and P₂O₅=0.22. (The total of these is 99.22 percent). All other constituents occur in very small quantities, usually much less than one percent.

The oxides combine in various ways. Some examples are given below.

§                     Potash and soda combine to produce mostly feldspars, but may also produce nepheline, leucite, and muscovite.

§                     Phosphoric acid with lime forms apatite.

§                     Titanium dioxide with ferrous oxide gives rise to ilmenite.

§                     Magnesia and iron oxides with silica crystallize as olivine or enstatite, or with alumina and lime form the complex ferromagnesian silicates (such as the pyroxenes, amphiboles, and biotites).

§                     Any silica in excess of that required to neutralize the bases separates out as quartz; excess alumina crystallizes as corundum.

These combinations must be regarded only as general tendencies, for there are numerous exceptions to the rules. The prevalent physical conditions also play a role in the formation of rocks.

Clarke also calculated the relative abundances of the principal rock-forming minerals and obtained the following results: apatite=0.6 percent, titanium minerals=1.5 percent, quartz=12.0 percent, feldspars=59.5 percent, biotite=3.8 percent, hornblende, and pyroxene=16.8 percent, for a total of 94.2 percent. These figures, however, can only be considered rough approximations

Human Progress

          Human progress

           

           Some milestones in scientific evolution:

    500BC -Indians produced steel.

1168  -Oxford University is founded in  England [ first university of the world]

1222      -Padua University is founded in Italy.

1242      -Naples University is founded in Italy, Cambridge University in England,   -Toulouse University in France, Rome University in Italy are founded.    

            Italy England and France became the study centers of western world.

1620    scientific method of reasoning expounded by Francis Bacon in his          Novum Organum

1650    Leydon University in the Netherlands set up the first chemistry laboratory.

1661    Robert Boyle defined an element as any substance that can not be broken      down into still simpler substances.

1755    Joseph Black discovered carbon dioxide.

1774    Joseph Priestly discovered oxygen.

1781    Henry Cavendish showed that water is a compound.

1808    John Dolton publishes his atomic theory.

1869    Mendeleyev—periodic table of elements (based on atomic mass).

1897    the electron was discovered by J J Thomson.

1932    Quantum model of the atom by Chadwick.

Atoms: - atom is the basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons.

All things are made up of atoms [atoms are smallest particles of matter, which can not be sub divided]. Atom consists of a central nucleus around which electrons revolve like planets revolve the sun. Electrons are charged particles. The nucleus consists of protons and neutrons as a solid mass bonded by strong nuclear force. Protons are positively charged particles. Size of nucleus is of the order of 10^-15 meter and the size of the atom is

10^-10 meter. Most of the atom is empty space. Atoms are building blocks of matter.

Each atom is associated with an atomic number [Z]. The number of protons it contains is defined as atomic number. Similarly each atom is associated with an atomic mass number [A]. The total mass of its constituent protons and neutron is atomic mass number.

Charge on electron=1.602x10^-19 coulomb.  = charge on proton also.

Mass of electron= 9.1 x 10^-31 kg.

Mass of proton = 1.6726 x 10^-27 kg.

Mass of neutron = 1.6749 x 10^-27 kg.

One Joule = 6 x10¹⁸ eV

Elements: An element is a substance which can not be further reduced to simpler substance by ordinary process, and is made up of particles [atoms] of one kind only.

Element is made up of same type of atoms grouped together. Example:- iron, gold, copper, aluminum oxygen etc.

Elements can exist as solids, liquid or gas. Elements are represented by symbols.

Two or more types of elements combine chemically in a fixed ratio to form compounds.

1. When iron power and Sulphur powder are mixed and heated sufficiently, they combine chemically to form iron sulfide. The process is irreversible

Fe + S → FeS.

2. When magnesium metal is burnt in air, it forms into a white powder.

The mass of the powder formed is greater than the mass of metal used.

Mg + O → MgO

3. Phosphorous reacts with oxygen to form phosphorous pentoxide. This is exothermic reaction in which energy is given out as light.

4P + 5O₂ → P₄O₁₀

Compounds:

Two or more elements combine in a fixed proportion to form a compound.  Symbols are used to represent compounds. The chemical change is written using equations of balanced atoms.

Two grams of hydrogen and 16 grams of oxygen combine to form 18 grams of water. Or two moles of hydrogen gas combines with one mole of oxygen gas to form two moles of water. Or two atoms of hydrogen combine with one atom of oxygen to form one water molecule H2O.

Properties of a compound are independent of the properties of constituent elements of which it is made up of. Compounds can exist as solids liquids or gases.

Compounds can not be separated easily.

Concept of molecule:

Similar types of atoms may combine to form molecules. Example: - the gases like hydrogen, oxygen or nitrogen have molecules as; H2, O2, N2.

Two or more atoms combine to form molecules. Different elements chemically combine to form compounds. A molecule of a compound has a fixed proportion of constituent elements atoms. Examples: - ammonia, carbon dioxide, and nitric acid have the molecular formula; NH3, CO2, HNO3 respectively.

            Atom, the basic unit of an element, has a symbol, an atomic number and a mass number. These atomic symbols are used to represent a compound. H₂O stands for water; C₆H₁₂O₆ stands for glucose, CO₂ for carbon dioxide and so on. They are called molecular formulae for compounds. Thus the branch of knowledge, the chemistry is developed.

Laws of chemical combination:

1789    law of conservation of mass      -Antoine Lavoisier

            Law of definite proportion         - Joseph Proust

1803    law of multiple proportion         -Dalton

1805    Dalton’s theory of Atom

1808    law of gaseous volume  -Gay Lussac

1811    Avogadro Law and concept of Mole

1919    atomic number and atomic mass number

1926    Quantum Mechanics model of Atom; quantum numbers n, l, m, s and

            Electronic configuration of atoms.

Dalton’s theory:1805

• All the atoms of a given element have identical properties including identical mass. Atoms of different elements differ in mass.
• Compounds are formed when atoms of different elements combine in a fixed ratio.
• Chemical reactions involve reorganization of atoms. These are neither created nor destroyed in a chemical reaction.

J. J. Thomson’s experiments on cathode [1897] rays proved the universal truth that all atoms contain negatively charged particles called electrons. He also found the value of charge to mass, e/m of an electron.

Milliken’s oil drop experiment gave the charge on the electron. And combining the results of both of them gives the mass of electron.

Thus the first sub-atomic particle electron with its mass and charge was established.

Electronic configuration of an atom:

Principle quantum numbers:                               n =  1   , 2 ,      3          …..

Orbital:                                                 s           p          d          f

Number of maximum electrons:             2          6          10        14

 1.        Hydrogen:                                            1s1

 2.        Helium:                                                1s2

 3.        Lithium:                                               1s2       2s1

 4.        Beryllium:                                            1s2       2s2

 5.        Boron:                                                  1s2       2s2 2p1

 6.        Carbon:                                                1s2       2s2 2p2

 7.        Nitrogen:                                              1s2       2s2 2p3

 8.        Oxygen:                                                1s2       2s2 2p4

 9.        Fluorine:                                               1s2       2s2 2p5

10.       Neon:                                                   1s2       2s2 2p6

11.       Sodium:                                                1s2       2s2 2p6            3s1

12.       Magnesium                                           1s2       2s2 2p6            3s2

13.       Aluminum                                             1s2       2s2 2p6            3s2 3p1

14.       Silicon                                                  1s2       2s2 2p6            3s2 3p2

15.       Phosphorus                                          1s2       2s2 2p6            3s2 3p3

16.       Sulphur                                                1s2       2s2 2p6            3s2 3p4

17.       Chlorine                                               1s2       2s2 2p6            3s2 3p5

18.       Argon                                                   1s2       2s2 2p6            3s2 3p6

19.       Potassium                                             1s2       2s2 2p6            3s2 3p6  4s1

20.       Calcium                                                1s2       2s2 2p6            3s2 3p6  4s2

24        Chromium                                            1s2       2s2 2p6            3s2 3p6  3d5    4s1

25        Manganese                                           1s2       2s2 2p6            3s2 3p6  3d5    4s2

26        Iron                                                      1s2       2s2 2p6            3s2 3p6  3d6    4s2     

27        Cobalt                                                  1s2       2s2 2p6            3s2 3p6  3d7    4s2

28        Nickel                                                  1s2       2s2 2p6            3s2 3p6  3d8    4s2

29        Copper                                                 1s2       2s2 2p6            3s2 3p6  3d10  4s1

30        Zinc                                                     1s2       2s2 2p6            3s2 3p6  3d10  4s2     

And the list grows up to all known elements.

The spectral lines explain the electronic configuration of that particular type of element.

                                         PERIODIC TABLE OF ELEMENTS

H																	He
1																	2
Li	Be											B	C	N	O	F	Ne
3	4											5	6	7	8	9	10
Na	Mg											Al	Si	P	S	Cl	Ar
11	12											13	14	15	16	17	18
K	Ca	Sc	Ti	V	Cr	Mn	Fe	Co	Ni	Cu	Zn	Ga	Ge	As	Se	Br	Kr
19	20	21	22	23	24	25	26	27	28	29	30	31	32	33	34	35	36
Rb	Sr	Y	Zr	Nb	Mo	Tc	Ru	Rh	Pd	Ag	Cd	In	Sn	Sb	Te	I	Xe
37	38	39	40	41	42	43	44	45	46	47	48	49	50	51	52	53	54
Cs	Ba	La	Hf	Ta	W	Re	Os	Ir	Pt	Au	Hg	Tl	Pb	Bi	Po	At	Rn
55	56	57	72	73	74	75	76	77	78	79	80	81	82	83	84	85	86
Fr	Ra	Ac	Ku	Ha
87	88	89	104	105
				Ce	Pr	Nd	Pm	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb	Lu
				58	59	60	61	62	63	64	65	66	67	68	69	70	71
				Th	Pa	U	Np	Pu	Am	Cm	Bk	Cf	Es	Fm	Md	No	Lr
				90	91	92	93	94	95	96	97	98	99	100	101	102	103

Classification of elements:-

Alkali Metals[s-block elements]   valence shell, s1 to s2

Non-metals and metalloids [p-block elements] valence shell, s2p1 to s2p6

Transition metals [d-block elements] valence shell d1s to d10s

Inner transition elements [f – block elements] Valence shell, f1ds to f10 ds.

Chemical properties are due to the arrangement of valence electrons in a molecule.

Metals are good conductors due to metallic bond formation among atoms.

The non-metals are bad conductors due to the formation of covalent bonds.

Ionic bonds are responsible for the formation of salts and oxides of metals.

The crystal can be either ionic or covalent in nature.

Hydrogen bonds bond the molecules with less force and can be broken easily.

Radio activity:

Uranium has two isotopes U238 and U235. Their percentage is 99% and 0.78% respectively. Half-life is billion years. When a high-energy neutron bombards the nucleus of isotope U235, it absorbs the neutron and becomes U236 which is unstable and the nucleus breaks down into two parts releasing multiples of neutrons outside the split matter. This can trigger the split of neighboring atoms and a chain reaction can be achieved to produce a bomb(an explosion), and if this reaction is controlled, it can be used to generate electric power. Thus nuclear power plants are built.

Plutonium has also two isotopes; Pu 239 [half-life 2400 years] and Pu 238 [half-life 80 years]. Pu 239 when bombarded with high-velocity neutrons, it breaks to release energy.

The natural uranium U 238 when bombarded with neutrons gets converted into Pu239 which can be used to release energy by specific techniques.

Fission reaction: it is a chain reaction that produced millions of neutrons within a very short time and a high-energy explosion occurs to destroy the neighborhood.

Chemistry is all about understanding the nature of atoms and the formation of bonds.

Atoms can share electrons to form molecules.

Example:- H2, O2, N2, CO2 [covalent bond formation]

            H─H,  O═O, N≡N,  O═C═O

Atoms can donate electrons to form molecules.[transfer of electrons]

Example:- NaCl , NaOH, CaCO₃, NH₄OH [ ionic bonds]

            Na⁺ Cl^-   Na⁺ OH^-    Ca²⁺CO₃^2-        NH4⁺OH^-                

Sodium donated its outer shell electron to chlorine and both have now eight electrons in their outer shell and therefore they are stable.

The earth's atmosphere has N2, O2, CO2, and H2O molecules as gases.

Sea water is H2O with many dissolved compounds like NaCl, MgCl2, CaCl2, MgSO4 CaSO4, etc. Water is a polar molecule and a good solvent.

When oxides of non-metals dissolve into water, the water becomes acidic due to an excess of H+ ions in water. [Acid is formed]. The acids are more reactive.

When hydroxides dissolve in water, the water becomes basic due to an excess of OH- ions.

[Base is formed]. The bases are more reactive.

Therefore compounds can form by;

• Only covalent bonds.
• Only ionic bonds.
• By a combination of both, covalent and ionic bonds.

Every reaction in the world can be written in the form:

Reactants -> Products

aA + bB -> cC + dD

Stoichiometry is the relationship between quantities of matter in a chemical reaction.

Avagadro’s number is the chemist’s dozen.  It’s used everywhere.  One “mole” contains 6.02 x 10^23 atoms, molecules, grains of sand, geese, or whatever you like.  You can talk about a mole of sand grains or a mole of people. 

The standard is 1 mole of carbon weighing 12 grams.  This is carbon isotope 12 only.  One amu or atomic mass unit is one twelve the molar mass of carbon.

1 amu = 1.66 * 10^ -24 grams

6.022 x 10^23 amu = 1 gram

55 moles of water = 1 liter

22.4 L = 1 mole of gas

A mole of gold weighs much more than a mole of oxygen.  They just have the same number of atoms.

Molecules in chemical reactions are not conserved, nor are the number of moles.  Mass is.  This is the law of mass action.  The accountant approach:  Mass In = Mass Out.

Exothermic reactions release heat.  Endothermic reactions take in heat.  Not the same as activation energy.

Avogadro’s number  = 6.02 x 10^23 = 1 mole

At standard temperature and pressure, 1 mole of any gas is 22.4 liters.

G = H – TdS

G is Gibbs Free Energy

G=0 the reaction is at equilibrium, sitting there, looking at you.  Could be a dynamic equilibrium or a static equilibrium. 

G (-) the reaction is spontaneous

G(+) you have to kick the reaction to make it go – add heat, catalyst, reagents, etc

Boron:

Boron is a typical nonmetal. It mainly occurs as Ortho-Boric acid [H3BO3], Borax [Na2B4O7.10H2O], and Kernite [Na2B4O7.4H2O]. There are two isotopes B¹⁰ [19%], and B¹¹ [81%]. Borax is a white crystalline solid also written as Na2[B4O5(OH)4].8H2O. Borax dissolves in water to give an alkaline solution.

            Na2B4O7 + 7H2O → 2NaOH  + 4H3BO3.

On heating borax loses water molecules and swells up.

            Na2B4O7.10H2O → Na2B4O7 → 2NaBO2 + B2O3

[B4O5(OH)4]^2-  anion  structure.

The BCl₃ molecule:

The sp² hybrid orbitals of boron are directed towards the comers of equilateral triangles and lie in a plane. Each of the sp2 hybrid orbitals of boron overlaps axially with the 3p-half-filled orbital of the chlorine atom to form three B-Cl sigma bonds.

           

The BCl₃ molecule

Boron trichloride is an inorganic compound with the formula BCl₃. This colorless gas is a valuable reagent in organic synthesis. It is highly reactive towards the water.

BCl₃ hydrolyzes readily to give boric acid:

BCl₃ + 3 H₂O → B(OH)₃ + 3 HCl

It unites readily with ammonia gas forming a white crystalline solid of composition 2BC13.3NH3.

Hydrated Iron(III) oxide:

Iron (III) oxide is a product of the oxidation of iron.

4 Fe + 3 O₂ + 2 H₂O → 4 FeO(OH)

The resulting hydrated iron(III) oxide, written here as Fe(O)OH, dehydrates around 200 °C.^[6][7]

2 FeO(OH) → Fe₂O₃ + H₂O

It can also be prepared by the thermal decomposition of Iron (III) hydroxide under temperature above 200 °C.

2 Fe(OH)₃ → Fe₂O₃ + 3H₂O

Industrial chemistry:

The Bayer Process for the production of Al₂O₃

In the Bayer process, bauxite is digested by washing with a hot solution of sodium hydroxide, NaOH, at 175 °C, under pressure. This converts the aluminum oxide in the ore to soluble sodium aluminate, 2NaAl(OH)₄, according to the chemical equation:

Al₂O₃ + 2 NaOH + 3 H₂O → 2 NaAl(OH)₄

This treatment also dissolves silica, but the other components of bauxite do not dissolve. Sometimes lime is added here, to precipitate the silica as calcium silicate. The solution is clarified by filtering off the solid impurities, commonly with a rotary sand trap, and a flocculent such as starch, to get rid of the fine particles. The mixture of solid impurities is called red mud. Originally, the alkaline solution was cooled and treated by bubbling carbon dioxide into it, through which aluminum hydroxide precipitates:

2 NaAl(OH)₄ + CO₂ → 2 Al(OH)₃ + Na2CO3 + H₂O

But later, this gave way to seeding the supersaturated solution with high-purity aluminum hydroxide(Al(OH)₃) crystal, which eliminated the need for cooling the liquid and was more economically feasible: NaAl(OH)₄ → Al(OH)₃ + NaOH

Then, when heated to 980°C (calcined), the aluminum hydroxide decomposes to aluminum oxide, giving off water vapor in the process:  2 Al(OH)₃ → Al₂O₃ + 3 H₂O

The left-over NaOH solution is then recycled. This, however, allows gallium and vanadium impurities to build up in the liquors, so these are extracted.

For bauxites having more than 10% silica, the Bayer process becomes infeasible due to insoluble sodium aluminum silicate being formed, which reduces yield, and another process must be chosen.

A large amount of the aluminum oxide so produced is then subsequently smelted in the Hall–Héroult process in order to produce aluminum

In the Hall–Héroult process alumina, Al₂O₃, is dissolved in an industrial carbon-lined vat of molten cryolite, Na₃AlF₆ (sodium hexafluoroaluminate), called a "cell". Aluminum oxide has a melting point of over 2,000 °C (3,630 °F) while pure cryolite has a melting point of 1,012 °C (1,854 °F). With a small percentage of alumina dissolved in it, cryolite has a melting point of about 1,000 °C (1,830 °F). Some aluminum fluoride, AlF₃ is also added into the process to reduce the melting point of the cryolite-alumina mixture.

The molten mixture of cryolite, alumina, and aluminum fluoride is then electrolyzed by passing a direct electric current through it. The electrochemical reaction causes liquid aluminum metal to be deposited at the cathode as a precipitate, while the oxygen from the alumina combines with carbon from the anode to produce carbon dioxide, CO₂. An electric potential of three to five volts is needed to drive the reaction, and the rate of production is proportional to the electric current. An industrial-scale smelter typically consumes hundreds of thousands of amperes for each cell.^[1][2]

The Most Common Minerals

• QUARTZ is undoubtedly the single most common mineral in the Earth's crust, ranging from perhaps 12% of continental crust to as much as 50% of oceanic crust as indicated by the composition of spreading-ridge volcanic lavas.  Some estimates place quartz at 21% of the Earth's total lithosphere.
• FELDSPAR, (a group of related minerals) comprises the bulk of the Earth's crust, approximately 60% of the continental crust or 49% of the lithosphere.  Perhaps 75% of this is the plagioclase feldspars (mostly albite, oligoclase and labradorite) with the remainder as potassium feldspars (mostly microcline and orthoclase).
• MICA (another group, primarily the minerals muscovite and biotite) comprises about 8% of the crust.
• OLIVINE (another group) is special. It's average composition mimics that of the bulk of the Earth - the mantle, which is nearly 1800 miles thick. Therefore, olivine is the most common mineral in the Earth, nearly 80% by volume, and that is a lot of peridot. It is the dense interior rock that the crust floats upon. Olivine is a major component of hot-spot volcanic lavas. About 15% of the crust is composed of olivines or their weathering/decomposition products, the PYROXENES (mostly augite) and the AMPHIBOLES (mostly hornblende).
• CALCITE comprises about 4% of the Earth's crust (but a lower percentage of the total lithosphere since it is unstable at the high temperatures of the inner mantle). It is important to note that the bulk of the Earth's carbon dioxide is tied up as calcium carbonate, otherwise the Earth's atmosphere might be 100 times as dense as at present and consist mostly of carbon dioxide, much like Venus (and with a similar impact on the planet).
• MAGNETITE is perhaps 3% of the crust.
• IRON, at least as the native element, is a nearly negligible component of the crust and the mantle, but the core of the earth is composed of a mixture of iron and nickel, and is, of course, mostly liquid. The inner core, approximately 1600 miles in diameter, is solid and thus qualifies as a mineral.

laterite,  soil layer that is rich in iron oxide and derived from a wide variety of rocks weathering under strongly oxidizing and leaching conditions. It forms in tropical and subtropical regions where the climate is humid. Lateritic soils may contain clay minerals; but they tend to be silica-poor, for silica is leached out by waters passing through the soil. Typical laterite is porous and claylike. It contains the iron oxide minerals goethite, HFeO₂; lepidocrocite, FeO(OH); and hematite, Fe₂O₃. It also contains titanium oxides and hydrated oxides of aluminum, the most common and abundant of which is gibbsite, Al₂O₃·3H₂O. The aluminum-rich representative of laterite is bauxite

The most common copper minerals are:

Mineral	Formula	Appearance	% copper in mineral
Cuprite	Cu2O	Red, earthy	see Qn 2
Chalcocite	Cu2S	Dark grey, metallic	see Qn 2
Bornite	Cu5FeS4	Golden brown, metallic	63
Malachite	CuCO3Cu(OH)4	Bright green, earthy	58
Azurite	2CuCO3Cu(OH)4	Blue, glassy	55
Chalcopyrite	CuFeS2	Golden yellow, metallic	35

Shale [normally black stone, a sedimentary rock]:- Shale is a fine-grained sedimentary rock whose original constituents were clay (mineral particles < 0.002 mm) or mud (a mixture of water and clay). It is characterized by thin, usually parallel layers. The formation of shale is similar to sandstone. Shales contain very small, poorly connected pores.

Shales are typically composed of variable amounts of clay minerals and quartz grains and the typical color is gray. The addition of variable amounts of minor constituents alters the color of the rock. Black shale results from the presence of greater than one percent carbonaceous material and indicates a reducing environment. Black shale can also be referred to as black metal. Red, brown, and green colors are indicative of ferric oxide (hematite - reds), iron hydroxide (goethite - browns and limonite - yellow), or micaceous minerals (chlorite, biotite, and illite - greens).

                                  

Clays are the major constituent of shales and other mudrocks. The clay minerals represented are largely kaolinite, montmorillonite and illite. Clay minerals of Late Tertiary mudstones are expandable smectites whereas in older rocks especially in mid to early Paleozoic shales illites predominate. The transformation of smectite to illite produces silica, sodium, calcium, magnesium, iron, and water. These released elements form authigenic quartz, chert, calcite, dolomite, ankerite, hematite, and albite, all trace to minor (except quartz) minerals found in shales and other mudrocks.

Shales and mudrocks contain roughly 95 percent of the organic matter in all sedimentary rocks. However, this amounts to less than one percent by mass in an average shale. Black shales which form in anoxic conditions contain reduced free carbon along with ferrous iron (Fe²⁺) and sulfur (S^2-). Pyrite and amorphous iron sulfide along with carbon produce black coloration and purple.

Feldspar, is any of a group of aluminosilicate minerals that contain calcium, sodium, or potassium. Feldspars make up more than half the Earth’s crust, and professional literature about them constitutes a large percentage of the literature of mineralogy

Feldspars (KAlSi₃O₈ – NaAlSi₃O₈ – CaAl₂Si₂O₈) are a group of rock-forming tectosilicate minerals that makeup as much as 60% of the Earth's crust.

  In the classification of igneous rocks of the International Union of Geological Sciences (IUGS), the feldspars are treated as two groups: the alkali feldspars and the plagioclase feldspars. The alkali feldspars include orthoclase, microcline, sanidine, anorthoclase, and the two-phase intermixtures called perthite. The plagioclase feldspars include members of the albite-anorthite solid-solution series. Strictly speaking, however, albite is an alkali feldspar as well as a plagioclase feldspar.

   

Chert is a sedimentary rock consisting almost entirely of silica (SiO₂), and can form in a variety of ways. Biochemical chert is formed when the siliceous skeletons of marine plankton are dissolved during diagenesis, with silica being precipitated from the resulting solution. Replacement chert forms when another material is replaced by silica, e.g. petrified wood forms when silica-rich fluids percolate through dead wood and the silica precipitates to replace the wood. Chert can also form through direct precipitation from silica-rich fluids, e.g. agate is formed by the precipitation of silica in voids within a rock. Chert has the general physical properties  of quartz                                                                                                        

Quartz Quartz (Figure 2), which is usually called silica, is one of the most common minerals in the Earth's crust. Quartz is made up of silicon dioxide (SiO2) Quartz crystals are usually hexagonal and prismatic in shape. Pure quartz is colourless, although the presence of impurities may give a range of colours, such as violet, pink and orange. Quartz is the raw material for making glass.
Plagioclase feldspar Plagioclase feldspar is a sodium- or calcium-rich feldspar. The chemical composition ranges from sodium aluminum silicate, NaAlSi3O8 to calcium aluminum silicate, CaAl2Si2O8. Plagioclase feldspar crystals usually occur as stubby prisms. Plagioclase feldspar is generally white to grey and has a vitreous lustre. Plagioclase feldspar is an important industrial mineral used in ceramics.
Alkali Feldspar Alkali feldspar is another member of the family of feldspar minerals. Alkali feldspar (Potassium aluminium silicate (K,Na)AlSi3O8) are rich in alkali metal ions. Alkali feldspar crystals usually occur as stubby prisms. Alkali feldspar is commonly pink to white. Alkali feldspar is used as raw material to make porcelain.
Micas Micas are a family of silicate minerals. Micas are made up of varying amounts of potassium, magnesium, and iron, as well as aluminum, silicon, and water. Micas form flat, book-like crystals that split into individual sheets, separating into smooth flakes along the cleavage planes. They are common minerals in intrusive igneous rocks, and can also be found in sedimentary and metamorphic rocks. Biotite is a dark, black, or brown mica; muscovite is a light-colored or clear mica.			Figure 6: Muscovite.
Amphiboles Amphiboles are a family of silicate minerals. Amphibole minerals generally contain iron, magnesium, calcium, and aluminum as well as silicon, oxygen, and water. Amphiboles form prismatic or needle-like crystals. Amphibole is a component of many igneous and metamorphic rocks. Hornblende (Figure 7) is a common member of the amphibole group of rock-forming minerals.
Pyroxene Pyroxenes (Figure 8) are a family of silicate minerals. Pyroxene minerals generally contain magnesium, iron, calcium, and aluminum as well as silicon and oxygen. Pyroxenes form short or columnar prismatic crystals. Pyroxene is a component in many igneous and metamorphic rocks. Pyroxene crystals are commonly faceted as gemstones. For instance, precious jade (jadeite) is a pyroxene.
Olivine Olivine (Figure 9) is a silicate mineral. Olivine ((Mg,Fe)2SiO4) contains iron and magnesium. Olivine is a green, glassy mineral. Olivine is common in mafic and ultramafic rocks, but has not been found in Hong Kong. Clear and transparent olivine crystals are commonly faceted as gemstones.
Calcite Calcite is a carbonate mineral. Calcite is made up of calcium carbonate (CaCO3). Calcite is generally white to clear and is easily scratched with a knife. Calcite is a common sedimentary mineral that is the major component of calcareous sedimentary rocks such as limestone. The metamorphism of limestone produces marble.