1ELEMENTS, COMPOUNDS AND MIXTURESChapter 14Properties Physical changes Usually dependent on conditions New substance NOT createdhlh Chemical changes A reaction occurs Transforms in to something different that has new propertiesElements Substances not bonded to other types of atoms May be single atoms in elemental formula Au Gold Li Lithium May have more than one atom to make molecules of that substance O2oxygen N2 nitrogen Or be macromolecules: diamond crystals of CCompounds More than one type of atom in the molecule Has a Chemical Formula Sodium Chloride NaClAiNHAmmoniaNH3 Subscript tells how many of each (Subscript 1 is omitted)Classes of matter “Substances” MIXTURESProperties of Compounds Very different from elements of their composition SodiumShiny soft metalShiny soft metal, melts at 97oC Reacts violently with water Chlorine Boils at ‐34oC Toxic gasProperties of Sodium Opaque, soft shiny metal Very malleable: can be cut with knifeTarni shes rapidly in airTarni shes rapidly in air Melts at about 100OC Reacts violently with water, producing lye and hydrogenhttp://en.wikipedia.org/wiki/SodiumProperties of Chlorine Yellowish gas at room temperature Toxic to organisms at low concentrations Reacts readily with most other elements Characteristic odorhttp://www.amazingrust.com/Experiments/how_to/Cl2.htmlProperties of Sodium Chloride Clear, brittle solid at room temperature Melts at 800oC Not toxic—table salt Not reactive with waterhttp://dharaniexim.tradeindia.com/Exporters_Suppliers/Exporter19695.325973/Sodium-Chloride.html2Bonding of atoms mak es molecules The Formation of Ions and Ionic Bonds Types of bonds Metallic Bonds Covalent Bonds Polar Covalent Bonds• Molecular Polarity and Molecular AttractionsCauses of bonding Atoms bond together through their electrons Electrons behave as though they are contained within a series of seven concentric hllshells Outer shell electrons interact with electrons of other atoms These are the VALENCE electronsElectron Shells Maximum number of electrons in each shell is shown Inner shell fills up before next shell bi t tbegins to get electrons Full shells are most stableFull electron shells Outer electron shells of noble gases are fullSodium Ion Formation Ion: An atom that has lost or gained one or more electronsPeriodic tableElectrons shells in periodic table First three periodsElectron Dot Structur e A notation showing only the valence electrons surrounding the atomic symbolValence Electr on dot structure for elemen ts not in transition metal gr oups3Ion An atom, molecule, or compound with a different number of protons and electrons More protons: positive CAT ION THE t looks like a plus sign… More electrons: negative AN ION Negative has an N in the prefix Both are all one word: anion, cationIon formation Lose electrons more protons than electrons positive charge Gain electrons More electrons than protons Negative charge More than one can be lost or gained Determine by position in periodic tableIonic Bonds Electrical force of attraction between oppositely charged ionsIonic Bond Ratios Compounds form in ratios to neutralize charges Molecular IonsHOHH+H+ Typically formed by the loss or gain of a hydrogen ion, H+Hydronium ion, H3O+Water Hydrogen ionGroup s of atoms forming ions Molecular ions Bonds within group are covalentNaming compounds fir s t word Start with element more to the left side of periodic tableNaming compounds sec ond word Add the element more to the right on the periodic table, change suffix to –ideNaming compounds NaCl Sodium Chloride4Naming compounds Li2O Lithium OxideNaming compounds CaF2 Calcium FluorideNaming diff er ent compounds of same elements When more than one compound is formed from differing ratios of the same atoms, a prefix is added to distinguish themCarbon Dio ideCarbon Dioxide Carbon MonoxideNaming Common CompoundsSome have traditional names Water AmmoniaMethaneMethane Propane etc.Nonpolar Cov alent Bonds Electrons are shared evenly when the two atoms are the same elementPolar Covalen t Bonds•Shared unevenly when the bonded atoms are different elementsPolarity of covalent bonds Closer together on the periodic table, less polar bond Further apart on the periodic table, more polar bond Molecules are called ‘dipoles’ Ionic bonds are extremely polar—beyond
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