
States of Matter
SolidLiquidGasMineralStructure of an Atom
protonsneutronsquarksatomic numberatomic mass numbereight most abundant elements in the Earth"s crust1s (max = 2) Total = 2 | L | 2s (max = 2), 2p (max = 6) Total = 8 | M | 3s (max = 2), 3p (max = 6), 3d (max = 10) Total = 18 |
Chemical Bonding
Most elements in the Earth react to form compounds although there are a few which are stable as elements (gold, for example). There are several "bonding models" which need to be summarized.Ionic Bonding - Element 11 (Sodium) has a single valence electron which can be relatively easily lost as it is relatively far from the positive charges in the nucleus. Oxygen needs (atomic number 8) needs two electrons to give it full s and p subshells. The compound Na2O consists of two Sodium cations and one Oxygen anion. Each Sodium contributes a single electron to the Oxygen giving the Oxygen a charge of -2. This compound is "held together" by ionic bonds.Covalent Bonding - Carbon contains 6 electrons and 4 of them are in the outer most level (the L level). Two carbons could bond by sharing their four electrons which would create the full s and p subshells in the L main shell. Covalent bonding involves sharing electrons.Metallic Bonding - Metals are known for their ability to conduct the flow of electrons. Metallic Bonding involves a "smearing out" of the valence electrons of the metal atoms. These electrons are easily displaced.van der Waals Bonding The carbon atoms in graphite are covalently bonded to form sheets of carbon atoms. The sheets are held together by weak attractive forces. The Periodic Table provides a framework in which to place thechemical elements so that their similarities are recognized. Look at the properties of Oxygen and Silicon - the two most abundant elements in the Earth"s crust - by clicking on their symbols on the Periodic Table. The recognition that the elements could be arranged in a systematic way so as to emphasize relationships between elements, was a major break through in the history of chemistry. For example, all of the elements in the first column (the alkali metals) have a singleoutermost electron in its outermost sub shell (an s sub shell).All of these elements can lose a single electron forming a cation with a +1 charge. All of the elements in the column on the far right (inert or Nobel gases) have two s electrons and eight p electrons in their outermost level (called the valence level). Note that the Periodic Table has the shape of a distorted "H". The vertical bars (sides of the H) contain the A group elements. The central bar contains the "transition" elements. Down at the bottom of the page are two rows - the "Lanthanides" and the "Actinides". Look to see where these rows fit into the "H". If these rows which shown in proper position the Periodic Table would be less compact.The Chemical Composition of the Continental Crust
Eight elements make up about 99% of the weight of the continental crustOxygen ~ 50%Silicon ~ 25%AluminumIronCalciumSodiumMagnesiumPotassiumMineral Structures
Think about the statement that oxygen occupies 95% of the volume of the Earth"s crust. If oxygens were cubes they could be packed together to fill up space. However, the oxygens are presumed to be spheres and you cannot pack equal sized spheres to fill up all space; some open spaces will remain inside of the framework produced by the oxygens. Other ions fit into these open spaces. In general, these spaces are "regular".

Classification of Minerals
The broadest classification of the nearly 3,500 known minerals is based on chemical composition. Thus, we recognize Native Elements (individual chemical elements), Carbonates (containing the CO3 group, Silicates (containing Silicon and Oxygen) and other broad chemical groups. Chemically, the silicates are very complicated and not much progress was made in understanding until a structural classification was devised. The most common "structural element" is the silicon/oxygen tetrahedron. The simplest structural class of silicates consists of those compounds (minerals) which consist of isolated single tetrahedra - the Nesosilicates. Tetrahedra can share oxygens between themselves. Two, three and four oxygens per tetrahedron can be shared and in some structures two or more sharing schemes exist. The most common minerals are listed below. (keep in mind that all of these contain Si and O and many also contain Al).MineralStructural TypeCompositionOlivine Isolated Fe and Mg richPyroxene Single Chains Ca, Fe, and Mg richAmphibole Double Chains Ca, Fe, Mg and K rich (with "OH")Mica Sheet Silicates K, Na rich (with "OH") Plagioclase Tectosiicates Ca and Na rich Alkali Feldspar Tectosilicates Na and K rich Quartz Tectosilicates SiIn addition, the following mineral groups are important - especially in the sedimentary rocksCarbonatesSulfatesSalts Silicate Structural Classification.Questions
Use the section on Properties to help answer the following questions.Distinguish between fracture and cleavageWhat is luster?Quartz has a hardness of 7 and Talc has a hardness of 1. Is Quartz seven times harder than Talc? Explain what type of scale Moh"s Scale is and how to use it. How is a diamond "cut"?