Week 10, Book Notes
Week 10, Book Notes Chem 141
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This 0 page Class Notes was uploaded by Cassidy Zirko on Sunday November 8, 2015. The Class Notes belongs to Chem 141 at University of Montana taught by Mark Cracolice (P) in Fall 2015. Since its upload, it has received 30 views. For similar materials see College Chemistry 1 in Chemistry at University of Montana.
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Date Created: 11/08/15
Chem 141 Prof Cracolice Week 10 book notes Chapter 27 How do Atoms Combine to Form Ionic Compounds and Molecules 11615 271 Why do Cations Attach to Anions Chemical bond forces that hold atoms together to form molecules or polyatomic ions hold atom together in metals or that hold oppositely charged ions together to form ionic compounds First contact is between the outer most electron of two particles Outer most electrons I valance electrons Valance electrons form bonds between two atoms How are Monatomic Ions that Are Isoelectric with a Noble Gas Atom Formed 0 Ho 0020000 0 Elements can form monatomic ions by gaining or loosing valance electrons until they become isoelectric I octet of electrons is complete Cation atoms loses one or more electrons positive charge Anion gains electrons I ion is negatively charged H doesn t normally exist by itself Hydronium ion hydrated hydrogen ion I H3O do Compounds form From Metal Ions and Nonmetal Ions Gaining or losing electrons not a common event Ionic Compounds Compounds made up of ions or solutions of ionic compounds Sodium and chlorine I sodium becomes positive chlorine is full I NaCl crystal Ions are not always present in a 11 ratio Combinations of charges appear in ionic compounds always in combinations so the overall charge is neutral Crystal ions arranged so potential energy resulting from the attractions and repulsions between atoms are at a minimum Crystals depend on the kind of ions compounds sizes and ratio Ionic Bonds strong electrostatic forces that hold the ions in fixed position in the crystal not limited to monatomic ions polyatomic ions can also forms ions bonds in a crystal are very strong nearly all ionic compounds are solids at room temperature substances melted or dissolved I crystals are destroyed liquid ionic compounds and water solutions of ionic compounds are good conductors 272 Why do Nonmetal Atoms Attach to One Another Ionic bonding explains properties of many compounds Chem 141 Prof Cracolice Week 10 book notes 0 How do Atoms Chare electrons O 0000 0000 Molecular Compounds ultimate structural unit is an individual particle molecule Physical and chemical properties of a molecules are different from properties that make up molecules Covalent bond shares one or more pairs of electrons between 2 or more nonmetals Attract both positively charged nuclei and couple the atoms to each other Bond is permanent until broken by a chemical change Simplest molecules are the simple covalent bond that appears Dots or straight lines between the two atoms represents the covalent bond that holds an atom together Electron cloudCharge density two electrons that are concentrated in the region between 2 nuclei Overlap atomic orbitals of the separated atoms Between two nuclei both nuclei are attracted to the electrons Electrons link nuclei together I electrons are the glue that bonds atoms to each other Lewis diagrams Lewis formulas Lewis structures show bonding arrangement between atoms in a molecule Unshared electrons should always be shown Lone pairs unshared electron pairs Electrons effectively belong to both atoms I valance electrons for both atoms Octet rule outer most orbital has 8 total electrons Stability of a noble gas electron configuration I minimization of energy associated with the configuration Tendency of complete octets re ect natural tendency of a system to move the lowest energy state possible 0 How do Atoms share More than One Electron Pair 0 00000 0 Single Bond sharing one pair of electrons Double bond sharing two pairs of electrons Triple bond bonded by three pairs of electrons Most abundant with triple bonds is N2 Multiple bond general term that includes double and triple bond Triple bond strong and distance between bonded atoms is shorter than the same measurement for a double bond between the same atoms Bond strength energy required to break a bond 0 How do Multi Atom Molecules Form 0 O 0 Hydrogen atoms forms bonds with one of 2 unpaired valance electrons in oxygen 2nd hydrogen does the same with the second unpaired valance electron in oxygen Carbon can make up to four bonds Poly atomic molecules contain multiple bonds 273 How are Bonding Electrons Shared between Nuclei Chem 141 Prof Cracolice Week 10 book notes 0 Nonpolar bond a bond in which bonding electrons are shared equally 0 Polar bond a bond in which bonding electrons are shard unequally 0 Negative charge density is closer to F39 I has negative pole 0 Charge density shift is extreme bonding electrons are effectively transferred to one atom I Ionic Bond 0 Electronegativity ability of an atom of that element in a molecule to attract bonding electron pairs to itself 0 High electronegativity I elements with strong attraction for bonding electrons 0 Electronegativities I greater at top of group I small atom bonding electrons closer to nucleus attracted more strongly 0 Increases from left to right I increasing nuclear charge among whose bonding electrons are in the same principle energy level 0 Highest in upper right region of periodic table 0 Estimate polarity of bond calculating difference in electronegativity values for bonded elements 0 Greater difference more polar bond 0 More electronegative toward which bonding electrons are displaces acts as the negative pole in a polar covalent bond 0 Arrow point towards negative pole HF Z Z v 0 Also can be wr1tten w1th pos1t1ve and negat1ve ab 139 0 Partial negative and partial positive charge less than the full charge found on ions