Lecture 4 Atoms, elements & minerals (oh my!)QuestionsRock typesWhat are Rocks…What is a mineral and why do we care….States of Matter (anything that has mass and occupies space)MineralsParts of atomsHow atoms relate to elementsSlide 10Isotopes of CarbonAtomic tendencies (Think Second Law of Thermodynamics)Slide 13Electrons and their shellsSlide 15Slide 16Noble gasesTherefore…The loss or gain of electrons (or the need to fill or empty shells)Example: Na and ClNa readily gives up the electron and becomes Na+ Cl readily gains an electron and becomes Cl-Na+ + Cl- = NaCl Sodium chloride, or saltIn other cases, electrons are shared between atoms to “fill” shellsAll bonds are not the sameThe mineral Graphite Chemical formula = CCompounds – bonded elementsIons and Atomic radiiSlide 28Slide 29Polymorphs: Minerals that have the same formula but different crystal structureComplex Ions (radicals)Slide 32Slide 33Slide 34Classification of mineralsSlide 36Slide 37Slide 38Slide 39Slide 40Slide 41Lecture 4Atoms, elements & minerals (oh my!)Questions•Why do elements become minerals?•Why are there such a variety of minerals?Outline:Atoms > elements > compoundsBondsMineral typesThe silica tetrahedralPhysical properties of mineralsRock types•Igneous–Volcanic (Extrusive)–Plutonic (intrusive)•Sedimentary–Clastic detrital–Chemical precipitates•Metamorphic–Regional–ContactWhat are Rocks…•Aggregate of mineralsWhat is a mineraland why do we care….•A mineral is:“Naturally occurring, inorganic solid with a specific chemical formula and definite crystal structure”Further, minerals are the basic building block of rocks (!!!!), as well as often being critical resources, themselves.Thus, we have to understand a bit of chemistry…..States of Matter(anything that has mass and occupies space)•Solid–Crystalline - atoms bond together in a regular orderly pattern–Amorphous - atoms bonded together in a random pattern•Liquid - atoms or molecules tightly packed but in random motion•Gas - particles in random motion at high speeds, separated by empty spaceMinerals•Naturally occurring inorganic solid, with a definite crystal structure and specific chemical formula–Must be solid with a crystal structure•Ice vs. water–Must be formed by a natural process•Natural vs. synthetic diamonds–Must be an inorganic compound•Coal is not a mineralParts of atoms•Nucleus–Protons & Neutrons•Electron shells–ElectronsHow atoms relate to elements•An element is defined by the number of Protons. This is called the atomic numberatomic number•The Atomic MassAtomic Mass of an element is simply the number of Protons + Neutrons•In general, there is about an equal number of Protons and Neutrons, but the number of neutrons can vary…•Elements that have several varieties of different mass are called IsotopesIsotopesIsotopes of CarbonSome isotopes are Stable (C-12, C-13)Others are Unstable (C-14) and spontaneously decayAtomic tendencies(Think Second Law of Thermodynamics)•Systems want to achieve lowest energy state•Elements need to be electrically neutral•Therefore, the positive charges realized from having Protons (+) must be balanced by an equal number of Electrons (-)Electrons and their shellsAtomic tendencies(Think Second Law of Thermodynamics)•Atoms, to be most stable, prefer:•Paired electrons•Completely filled outer shells•But we know that because the number of Protons (+) determine the number of Electrons (-), that all odd-numbered elements have unpaired electrons, and only 6 elements have completely filled shells…Each row starts newElectron ShellsEach column an electron is addedNoble gasesLast column hasCompletely filledElectron shells.These elements are non-reactiveand do not bondTherefore…•Elements that have unfilled shells may gain or lose electrons (fill or empty shells)•But, this in turn causes them to become “charged” atoms or IONS.•A positively charged atom (loss of electrons) = a CATION•A negatively charged atom (gain of electrons) = an ANIONSome atoms can gain or lose more than one electron. The numeric charge that results is calledVALENCE STATEDenoted by a + or a -Example: Iron can exist in several valence states,Fe2+, Fe3+The loss or gain of electrons(or the need to fill or empty shells)•Results in BONDING•Remember, atoms want to be electrically neutral•Thus, ions (charged atoms) will bond with one another forming COMPOUNDS•Or atoms may bond by sharing electrons in order to fill outer shells…Example: Na and ClNa is in first column. Has 1 unpaired electron in outer shellCl is in second to last column. Needs only one electron to complete shellNa readily gives up the electron and becomes Na+Cl readily gains an electron and becomes Cl-IONIC BONDINGAtoms attracted by opposite electrical chargeNa+ + Cl- = NaClSodium chloride, or saltAs a crystalline solid, geologists term this the mineral HALITEThis compound has a net charge = 0In other cases, electrons are shared between atoms to “fill” shellsCOVALENT BONDINGThe sharing of electronsAll bonds are not the same•Ionic bonding – electrostatic forces, can be broken (ex. dissolving salt in water)•Covalent bonding – very strong bonds, example: H2O; O2•Metallic bonds – freely moving electrons in outer shells. What do you call free flowing electrons?•van der Waals – weak electrostatic forces (not related to electrons)The mineral GraphiteChemical formula = CCovalent bonds join carbon atoms into “sheets”Sheets are held together byvan der Waals bondsCompounds – bonded elements•Compounds, then are:–Often neutral in overall charge•If existing as a solid, compounds have–Geometric “packing”–Exhibit “closest packing” (determined by the prevailing energy conditions during mineral formation)How do the atoms arrange themselves?By Size and ChargeIons and Atomic radii•Atomic radii–The distance from the center of nucleus to the outer electron shell–i.e. the “size” of an atom•Cations v Anions–Which is larger and why?•Cations lose electrons; Anions gain electrons•Size also determined by atomic number, the more Protons and Neutrons, then, the larger the atomNaClHALITECaCO3CALCITECrystal structure is a repeating geometric sequence beginning at the micro scale and continuing to macro scalePolymorphs: Minerals that have the same formula but different crystal structureComplex Ions (radicals)•In some cases, covalently