Mineral Chemistry GY111 Physical Geology Mineral Chemistry lecture for Physical Geology.

Atoms & Atomic Particles An atom is the smallest component of an element that can retain the properties of that element Atoms are composed of fundamental particles: Protons Neutrons Electrons Protons & Neutrons always reside in the center of the atom termed the nucleus Electrons are always located in the electron cloud (orbitals) where they orbit the nucleus 1. An atom is the smallest component of an element that can retain the properties of that element. 2. Atoms are composed of fundamental particles: Protons Neutrons Electrons 3. Protons & Neutrons always reside in the center of the atom termed the nucleus. 4. Electrons are always located in the electron cloud (orbitals) where they orbit the nucleus.

Example Atom: Carbon Carbon: contains 6 protons and 6 neutrons in the nucleus, and 6 electrons in 2 orbital shells Example element Carbon: contains 6 protons and 6 neutrons in the nucleus, and 6 electrons in 2 orbital shells. Innermost electron shell contains a maximum of 2 electrons. The second shell contains a max. of 8 electrons. In the Carbon example there are 4 electrons in the second outer shell.

Subatomic Particles Proton: has a mass of 1 and a positive charge Neutron: has a mass of 1 and a neutral charge Electron: has a mass of 0 and a negative charge All elements in the periodic table can be considered to have a neutral charge in their elemental form, therefore, they must have the same number of protons and electrons 1. Proton: has a mass of 1 and a positive charge. 2. Neutron: has a mass of 1 and a neutral charge. 3. Electron: has a mass of 0 and a negative charge. 4. All elements in the periodic table can be considered to have a neutral charge in their elemental form, therefore, they must have the same number of protons and electrons.

Periodic Table of the Elements Elements are identified by their atomic number (ex. Carbon = 6) The periodic table of elements uses abbreviations for chemical elements. For example “O” is oxygen, “Si” is silicon. The number in each square is the atomic number of the element. The atomic number matches the number of protons in the nucleus and the number of electrons in the elemental (un-bonded) state.

Atomic Number & Weight Atomic Number: the sum of the protons in the atom; The number uniquely identifies the element. Atomic Mass: the sum of the protons and neutrons in the nucleus of the atom Isotope number: same as atomic mass, C12: 6 protons and 6 neutrons in nucleus C14: 6 protons and 8 neutrons in nucleus 1. Atomic Number: the sum of the protons in the atom; The number uniquely identifies the element. 2. Atomic Mass: the sum of the protons and neutrons in the nucleus of the atom 3. Isotope number: same as atomic mass, C12: 6 protons and 6 neutrons in nucleus C14: 6 protons and 8 neutrons in nucleus

Isotopes The isotope number (also termed mass number) of an atom is the sum of the protons and neutrons. Isotope Carbon 14 has 6 protons and 8 neutrons. Isotope Carbon 12 has 6 protons and 6 neutrons. Chemists have determined that 99.99% of carbon atoms are C12, and most of the rest are C13 so on average the atomic weight of Carbon = 0.9999 * 12 + 0.0001 * 13 = 12.01 grams/mole. Isotope number (mass) = Number of Protons + Neutrons C14 = 6 protons + 8 neutrons C12 = 6 protons + 6 neutrons Note that all Carbon atoms must have 6 protons in nucleus. During chemical bonding elements that may bond with carbon cannot differentiate between C14 and C12 because the electrons shells are exactly the same. Atomic weight Carbon = 0.9999 * 12.0 + 0.0001 * 13.0 = 12.011 grams/mole.

Ions When an atom in its elemental state receives or gives up one or more electrons it is then termed an “Ion” Positively charged ions are cations Negatively charged ions are anions The ability to give up or take on electrons in an atom is dependent on the atomic number (i.e. the number of electrons in the electron shells) 1. When an atom in its elemental state receives or gives up one or more electrons it is then termed an “Ion”. 2. Positively charged ions are cations. 3. Negatively charged ions are anions. 4. The ability to give up or take on electrons in an atom is dependent on the atomic number (i.e. the number of electrons in the electron shells).

Electron Shell Configurations The first 3 electron shells are filled by 2, 8 and 8 electrons. A specific element is chemically stable when its outermost shell is completely filled by electrons In the Carbon example the outer shell needs 8 electrons but Carbon has only 4 in the outermost shell because of its atomic number of 6 (2 electrons in the 1st shell, 4 in the 2nd) Therefore Carbon will either have a +4 ionic charge if it gives up all the outer shell electrons, or a -4 charge if it receives 4 to fill the outer shell 1. The first 3 electron shells are filled by 2, 8 and 8 electrons. 2. A specific element is chemically stable when its outermost shell is completely filled by electrons 3. In the Carbon example the outer shell needs 8 electrons but Carbon has only 4 in the outermost shell because of its atomic number of 6 (2 electrons in the 1st shell, 4 in the 2nd). 4. Therefore Carbon will either have a +4 ionic charge if it gives up all the outer shell electrons, or a -4 charge if it receives 4 to fill the outer shell.

Rock-Forming Element Valence Oxygen (O): Atomic # = 8; 6 electrons in 2nd shell = -2 anion. Silicon (Si): Atomic # = 14; 4 electrons in 3rd shell = +4 cation. Aluminum (Al): Atomic # = 13; 3 electrons in 3rd shell = +3 cation. Iron (Fe): Atomic # = 26; 2 or 3 electrons in 4th shell = +2 or +3 cation (ferric or ferrous Fe). Magnesium (Mg): Atomic # = 12; 2 electrons in 3rd shell = +2 cation. Calcium (Ca): Atomic # = 20; 2 electrons in 4th shell = +2 cation. Sodium(Na) & Potassium(K): Atomic #’s = 11 & 19; 1 electron in outer shell = +1 cation. Valence state is controlled by electron shell configuration. Electrons are gained or lost to expose a “filled” outermost shell. In silicates O (oxygen) is the dominant anion and also the most abundant element in the crust and mantle. Other elements such as Al, Ca, Mg, etc. combine with Si and O to form the most abundant mineral group in the crust and mantle – the silicates. When a mineral formula is written it must me electrically nuetral: SiO2 ( Si 4+ and 2 * (O 2-) ) = net charge of 0.

Relationship of Electron Shells to Periodic Table The elements on the Periodic Table are arranged in columns of like electron shell configuration Example: The Alkali Earth metals (H, Li, Na, K, etc.) all have one electron in the outer shell Example: The Halogens (F, Cl, Br, etc.) all have 7 electrons in the outer most shell The Alkalis all tend to form +1 charged cations when bonding with other elements; The Halogens then to form -1 anions 1. The elements on the Periodic Table are arranged in columns of like electron shell configuration. 2. Example: The Alkali Earth metals (H, Li, Na, K, etc.) all have one electron in the outer shell. 3. Example: The Halogens (F, Cl, Br, etc.) all have 7 electrons in the outer most shell. 4. The Alkalis all tend to form +1 charged cations when bonding with other elements; The Halogens then to form -1 anions.

Chemical Bonding Ionic: loss or gain of electrons forming cations and anions (allows material to dissolve in a polar solvent such as H2O) Covalent: electron sharing in outer shell (strongest bond) Metallic: electron sharing in inner shell (allows for conduction of electricity) 1. Ionic: loss or gain of electrons forming cations and anions (allows material to dissolve in a polar solvent such as H2O). 2. Covalent: electron sharing in outer shell (strongest bond). 3. Metallic: electron sharing in inner shell (allows for conduction of electricity).

Ionic Bonding Example NaCl: note that Na (atomic number=11) will form a +1 cation, and that Cl (atomic number=17) will form a -1 anion. 1. NaCl: note that Na (atomic number=11) will form a +1 cation, and that Cl (atomic number=17) will form a -1 anion. 2. The Na and Cl ions fit together to form a cubic structure.

Covalent Bonding Example Diamond has strong covalent bonding in all direction by sharing electrons in the outer shell of each Carbon atom 1. Diamond has strong covalent bonding in all direction by sharing electrons in the outer shell of each Carbon atom. 2. Adjacent atoms contribute 2 electrons to complete the outer shell with 8 electrons.

Metallic Bonding Example Gold (Au) is the best conductor of electricity because of its metallic bonding 1. Gold (Au) is the best conductor of electricity because of its metallic bonding. 2. Metallic bonding allows sharing of electrons among many atoms throughout all electron shells. 3. Metallic bonded substances are opaque to light no matter how thin the layer of material may be.

Common Rock Forming Cations and Anions Cations: positively charged Anions: negatively charged Ionic Radius: size of the charged ion 1. Cations: positively charged. 2. Anions: negatively charged. 3. Ionic Radius: size of the charged ion. 4. Note that the larger the positive charge on the cation the smaller the ionic radius. 5. Anions are larger than cations.

Mineral Solid: cannot be liquid or gas. Inorganic: cannot be composed of living or once-living material. Naturally Occurring: cannot be man-made. Crystalline: possesses an ordered internal structure and a definite chemical composition. Mineral Definition 1. Solid: cannot be liquid or gas. 2. Inorganic: cannot be composed of living or once-living material. 3. Naturally Occurring: cannot be man-made. 4. Crystalline: possesses an ordered internal structure and a definite chemical composition.

Rock Forming Minerals Silicates: contain Si and O plus other rock forming elements Fundamental structure is SiO4 tetrahedron The geometry of how the tetrahedrons link controls the properties of the silicate mineral 1. Silicates: contain Si and O plus other rock forming elements. 2. Fundamental structure is SiO4 tetrahedron. 3. The geometry of how the tetrahedrons link controls the properties of the silicate mineral. 4. Fundamental SiO4 structures: Isolated: Olivine, no corners shared. Chain: Pyroxene, 2 corners shared. Double chain: Amphibole, 2 and 3 corners shared. Sheet: Mica, 3 corners shared. Framework: Quartz, 4 corners shared.

Other Major Rock Forming Mineral Groups Carbonates: CaCO3 (calcite) Oxides: Fe3O4 (magnetite) Sulfides: FeS2 (pyrite) Sulfates: CaSO4 (anhydrite) Halides: CaF2 (Fluorite) Rock forming mineral groups other than Silicates: 1. Carbonates: CaCO3 (calcite) 2. Oxides: Fe3O4 (magnetite) 3. Sulfides: FeS2 (pyrite) 4. Sulfates: CaSO4 (anhydrite) 5. Halides: CaF2 (Fluorite)

Physical Properties of Minerals Hardness Cleavage (Fracture) Luster (Metallic vs. Non-metallic) Vitreous: glassy Resinous: like tree sap Greasy: oily Pearly: like pearls Silky: like silk Adamantine: luster of diamond Color Specific Gravity Crystal Form (Habit) 1. Hardness 2. Cleavage (Fracture) 3. Luster (Metallic vs. Non-metallic) Vitreous: glassy Resinous: like tree sap Greasy: oily Pearly: like pearls Silky: like silk Adamantine: luster of diamond 4. Color 5. Specific Gravity 6. Crystal Form (Habit)

Moh’s Hardness Scale Scale allows for the determination of the hardness of a mineral 1. Moh’s Hardness Scale (memorize!)

Exam Summary For Exams know: Subatomic particle definitions Definitions of ion, cation, anion, isotope, atomic number, atomic weight Definitions and examples of ionic, covalent and metallic bonding Silicate structures and examples (i.e. isolated tetrahedra=olivine, chain=pyroxene, etc.) Chemical groups of rock-forming minerals and an example of each (Silicates=quartz, Carbonates=calcite; sulfides=pyrite, etc.) Moh’s Hardness scale Definition of physical properties of minerals (color, hardness, streak, etc.) 5 examples of industrial uses of minerals. Electron shell configuration and valence in rock forming elements. For Exams know: 1. Definitions of ion, cation, anion, subatomic particles, isotope number, atomic number, atomic weight. 2. Definitions and examples of ionic, covalent and metallic bonding. 3. Silicate structures and examples (i.e. isolated tetrahedra=olivine, chain=pyroxene, etc.). 4. Chemical groups of rock-forming minerals and an example of each (Silicates=quartz, Carbonates=calcite; sulfides=pyrite, etc.). 5. Moh’s Hardness scale. 6. Definition of physical properties of minerals (color, hardness, streak, etc.). 7. 5 examples of industrial uses of minerals. 8. Electron shell configuration and valence in rock forming elements.