Be sure to attend lab THIS week Water Chemistry Range of scales Bring the lab manual Must pass lab to pass this class Instructors will give percent lab grade to one another Electron cloud Atoms are the particles of matter All things composed of atoms Smallest particle that retains the properties of the element Nucleus Atom New Cle Us Too many people in important positions say it incorrectly do not show your ignorance by doing the same 1 Periodic Table Elements of the Crust Chemical Symbols First letter is capitalized Second letter if present is not capitalized SN is a compound of sulfur and nitrogen Sn is the element Tin Dot diagram of some elements Does not matter which side you start on One per side until there are four then add second one per side to a total of eight Oxygen Silicon Aluminum Iron Calcium Sodium Potassium Magnesium O Si Al Fe Ca Na K Mg 47 28 8 5 4 3 3 2 Dot Diagram Symbol for element Show valence electrons only Start with one per side Up to two per side Single element ions How do you know if it makes a negative or positive ion Look at the dot diagram to see if it will lose electrons or gain them Memorize positions in periodic table 1 far left 2 second on left 1 second from right 2 third from right 2 Element groups Chemical Formula of Ionic Compounds The columns of the periodic table Far right noble gases nonreactive Far left alkali metals extremely reactive 2nd on right halogens extremely reactive 2nd on left alkaline earth metals very reactive 3rd on right chalcogens oxygen family very reactive Find charges from periodic table Use subscripts to indicate how many of each Combine so the charges cancel to neutral Naming compounds Ionic Bonds with Dot Diagram Positive plus negative is zero crossover charges for subscripts Cations element name Anions element name changed to end with ide Ions are not electrically neutral Ions are not like the atoms they are derived from Sodium Chloride structure Periodic Table 3 Covalent Bonds Overlapping outer shells to make 8 electrons for each atom some are shared Silicate minerals have silicon and oxygen joined with covalent bonds Water is hydrogen and oxygen joined with covalent bonds Polar molecules Molecules formed by covalent bonds Like nonmetals form nonpolar covalent bonds Unlike nonmetals form polar covalent molecules Polar molecules have charge concentrated at one end Metals form metallic bonds not covalent bonds Electro negativity of selected elements Degree of polarity can be determined by difference of electronegativity of each element Further apart on periodic table greater polarity Water Molecule Bent molecule Covalent bonds Polar Dissolves ionic substances Properties of Water Solid water floats on liquid water High surface tension Universal solvent High specific heat High heat of vaporization 4 In liquid phase the water molecules fit closely together Polar nature allows them to attract one another Liquid water molecules Crystal structure of ice http www its caltech edu atomic snowcrystals primer primer htm In solid phase of water arrangement becomes more open less dense Ice floats because of this Expansion of 9 upon freezing http www chemlin net news 2007 mar2007 water htm High Surface Tension Dissolution of ionic substance http www webelements com nexus node 786 http quest nasa gov space teachers microgravity 6surf html Water phases and molecules Three phases at Earth s surface Liquid Solid Vapor Energy captured or released upon change from one phase to another 5
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