Metathesis Reactions Precipitation Reactions Molecular equation Ca NO3 2 aq K 2 CO 3 aq 2 KNO3 aq CaCO3 s 1 Metathesis Reactions Molecular equation 3 CaCl2 aq 2 Na 3 PO 4 aq 6 NaCl aq Ca 3 PO 4 2 s 2 Metathesis Reactions Molecular equation 2 HCl aq Na 2SO3 aq 2 NaCl aq H 2O SO 2 g 2H 2Cl 2Na SO3 2 2Na 2Cl H20 SO2 2H SO3 2 H20 SO2 Cl Na Spectator ions 3 Gas Formation Reactions A gas formation reaction is a type of reaction in which there is a formation of an insoluble or slightly soluble gas when there are no gaseous reactants Displacement reactions in which an active metal displaces from an acid or from water are gasformation reactions they are not metathesis reactions Only common gases that are very soluble in water are HCl and NH3 4 Gas Formation Reactions Consider hydrochloric acid with calcium carbonate to form carbonic acid Formula Unit 2HCl aq CaCO3 s H2CO3 aq CaCl2 aq Total Ionic 2 H aq Cl aq CaCO3 s H2CO3 aq Ca2 aq 2Cl aq Net Ionic 2H aq CaCO3 s H2CO3 aq Ca2 aq 5 Gas Formation Reactions Enough heat is generated in the reaction to cause thermal decomposition of carbonic acid H2CO3 aq CO2 H2O l The net effect of the chemical reaction and subsequent decomposition is 2HCl aq CaCO3 s CO2 H2O l CaCl2 aq 6 Ch 7 Chemical Bonding end of chapter problems partial list 1 2 4 6 8 10 16 20 23 24 30 38 44 46 52 57 Chemical bonding refers to the attractive forces that hold atoms together in compounds The electrons involved in bonding are usually those in the outermost valence shell 7 Chemical bonds are classified into two types o Ionic bonding results from electrostatic attractions among ions which are formed by the transfer of one or more electrons from one atom to another o Covalent bonding results from sharing one or more electron pairs between two atoms 8 Comparison of Ionic and Covalent Compounds Melting point comparison Ionic compounds are usually solids with high melting points Typically 400oC Covalent compounds are gases liquids or solids with low melting points Typically 300oC Solubility in polar solvents remember like dissolves like Ionic compounds are generally soluble Covalent compounds are generally insoluble 9 Solubility in polar solvents Ionic compounds are generally soluble Covalent compounds are generally insoluble Solubility in nonpolar solvents Ionic compounds are generally insoluble Covalent compounds are generally soluble Conductivity in molten solids or liquids Ionic compounds generally conduct electricity They contain mobile ions Covalent compounds generally do not conduct electricity 10 Conductivity in aqueous solutions Ionic compounds generally conduct electricity They contain mobile ions Covalent compounds are poor conductors of electricity Formation of Compounds Ionic compounds are formed between elements with large differences in electronegativity Often a metal and a nonmetal Covalent compounds are formed between elements with similar electronegativities Usually two or more nonmetals 11 Lewis Dot Formulas of Atoms The and arrangements of e in the outermost shells of atoms determine the chemical and physical properties of the elements as well as the kinds of chemical bonds they form Lewis dot formulas or Lewis dot representations are a convenient bookkeeping method for tracking valence electrons Chemical bonding involves only the valence e which are usually the e in the outermost occupied s and p orbitals They are chemically important 12 Table 7 1 p 252 Ionic Bonding Formation of Ionic Compounds Ionic bonding is the attraction of oppositely charged ions cations and anions in large numbers to form a solid Such a solid cpd is called an ionic solid An ion is an atom or a group of atoms possessing a net electrical charge Ions come in two basic types 1 positive ions or cations These atoms have lost 1 or more electrons 2 negative ions or anions These atoms have gained 1 or more electrons 14 Clicker Q How many valence e does Cl have Monatomic ions consist of one atom Examples Na Ca2 Al3 cations Cl O2 N3 anions Polyatomic ions contain more than one atom NH4 cation NO2 CO32 SO42 anions Clicker Q How many valence e does C have 15 Ionic bonds are formed by the attraction between cations and anions usually to form solids When the electronegativity difference EN between 2 elements is large as between a metal and a nonmetal the elements are likely to form a compound by ionic bonding Commonly metals react with nonmetals to form ionic compounds The formation of NaCl is one example of an ionic compound formation 16 2Li F2 2LiF The underlying reason for the formation of LiF lies in the electron configurations of Li and F 1s 2s 2p Li F These atoms form ions with these configurations Li same configuration as He F same configuration as Ne 17 We can also use Lewis dot formulas to represent the neutral atoms and the ions they form 18 The Li ion contains two electrons same as the helium atom Li ions are isoelectronic with helium The F ion contains ten electrons same as the neon atom F ions are isoelectronic with neon Isoelectronic species contain the same number of electrons 19 The reaction of potassium with bromine is another example of a group IA metal with a Group VIIA non metal Write the reaction equation then Lewis dot then e config 20 There is a general trend evident in the formation of these ions Cations become isoelectronic with the preceding noble gas Anions become isoelectronic with the following noble gas 21 In general for the reaction of IA metals and VIIA nonmetals the reaction equation is 2 M s X2 2 M X s where M is the metals Li to Cs and X is the nonmetals F to I Electronically this is occurring ns np ns np M M X X 22 Next we examine the reaction of IIA metals with VIIA nonmetals This reaction forms mostly ionic compounds Notable exceptions are BeCl2 BeBr2 and BeI2 which are covalent compounds One example is the reaction of Be and F2 Be s F2 g BeF2 g 23 The valence electrons in these two elements are reacting in this fashion 2s 2p 2s 2p Be He Be2 He F He F He Next draw the Lewis dot formula representation of this reaction 24 The remainder of the IIA metals and VIIA nonmetals react similarly Symbolically this can be represented as M s X2 M2 X2M can be any of the metals Be to Ba X can be any of the nonmetals F to Cl Remember the exceptions BeCl2 BeBr2 and BeI2 which are covalent compounds 25 For the reaction of IA metals with VIA nonmetals a good example is the reaction of lithium with oxygen The reaction equation is 26 Draw the electronic configurations for Li O and