Mineral Chemistry GY111 Earth Materials 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 Example Atom Carbon Carbon contains 6 protons and 6 neutrons in the nucleus and 6 electrons in 2 orbital shells 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 Periodic Table of the Elements Elements are identified by their atomic number ex Carbon 6 Atomic Number Weight Atomic Number the sum of the protons in the atom The number uniquely identifies the element Atomic Weight the sum of the protons and neutrons in the nucleus of the atom Isotope number same as atomic weight C12 6 protons and 6 neutrons in nucleus C14 6 protons and 8 neutrons in nucleus 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 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 below 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 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 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 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 Covalent Bonding Example Diamond has strong covalent bonding in all direction by sharing electrons in the outer shell of each Carbon atom Metallic Bonding Example Gold Au is the best conductor of electricity because of its metallic bonding Common Rock Forming Cations and Anions Cations positively charged Anions negatively charged Ionic Radius size of the charged ion 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 Other Major Rock Forming Mineral Groups Carbonates CaCO3 calcite Oxides Fe3O4 magnetite Sulfides FeS2 pyrite Sulfates CaSO4 anhydrite 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 Moh s Hardness Scale Scale allows for the determination of the hardness of a mineral Summary For Exams know Definitions of ion cation anion 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
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