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Learn how to name and identify chemical compounds and reactions, including covalent and ionic bonding. Understand the difference between metals and nonmetals and their electron behavior. Follow a flow chart to determine if a compound is ionic or covalent. Practice naming binary molecular compounds using prefixes and criss-crossing for ionic compounds. Determine formulas from names using charges.
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Ionic vs. Covalent, Nomenclature, and Chemical Reactions Naming and identifying chemical compounds and reactions
Covalent Bonding Covalent Bond: A bond that results when two atoms share several (usually two) electrons. Covalency is greatest between atoms when electronegativities are similar.
Ionic Bonding Ionic Bond: A bond that results when two atoms have exchanged electrons. Ionicity is greatest between atoms when electronegativities are significantly different.
Na + Cl2 Na+ + Cl– Ionic Bonds In the formation of sodium chloride, one electron is transferred from the sodium atom to a chlorine atom. 17 protons 17 electrons 11 protons 11 electrons 11 protons 10 electrons 17 protons 18 electrons Cation: A positively charged particle. Metals tend to lose electron(s) and form cations. Anion: A negatively charged particle. Nonmetals tend to gain electron(s) and form anions.
Metals vs. Nonmetals • Metals tend to have lowIONIZATION ENERGY They tend to lose one or more electrons. • Nonmetals tend to have highELECTRON AFFINITY They tend to gain one or more electrons.
Electronegativity For ionic compounds, you need large electronegativity differences between atoms. General rule is ionic bonds are formed between a metal (becomes cation when loses electron(s)) and a nonmetal (becomes anion when gains electron(s)). Electrons are “transferred”. For covalent compounds, you need minimal electronegativity differences between atoms. General rule is covalent bonds are formed between two nonmetals. Electrons are “shared”.
Ionic or Covalent? BaCl2 Cr(NO3)6 FePO4 CuSO3 Si2S4 N2O3 Al3N2 K3P
Prefixes 1 mono 7 hepta 2 di 8 octa 3 tri 9 nona 4 tetra 10 deca 5 penta 6 hexa 12 dodeca
Compounds containing semimetals are named like compounds containing all nonmetals (covalent compounds).
Worked Example Naming Binary Molecular Compounds Give systematic names for the following compounds: a. PCl3b. N2O3c. P4O7 d. BrF3 Strategy Look at a periodic table to see which element in each compound is more cationlike (less electronegative; farther to the left or lower) and which is more anionlike (more electronegative; farther to the right or higher). Then name the compound using the appropriate numerical prefix. Solution a. Phosphorus trichloride b. Dinitrogen trioxide c. Tetraphosphorus heptoxide d. Bromine trifluoride
Criss Cross: Going from Formula to NameCriss crossing is only used for ionic compounds that contain weird charges like transition metals. Group 1A and 2A metals, the charge is known and is +1 and +2, respectively. ALWAYS IDENTIFY THE COMPOUND AS IONIC OR COVALENT FIRST.
Criss Cross: With Transition Metal FeCl2 FeCl2 Fe2 Cl1 Fe+2 Cl-1 More electronegative species will carry negative charge meaning it will gain the electrons. Chlorine is in Group 7A and wants to get to 8. How many electrons will it gain? 1e Since Fe comes first and is the metal, it will have a positive charge (cation). Likewise, Cl comes second and will have a negative charge (anion). Criss Cross and add positive and negative sign. Iron is +2 so we give roman numeral of II. This is iron (II) chloride. iron (II) chloride
Criss Cross: With Transition Metal FeCl3 FeCl3 Fe3 Cl1 Fe+3 Cl-1 More electronegative species will carry negative charge meaning it will gain the electrons. Chlorine is in Group 7A and wants to get to 8. How many electrons will it gain? 1e Since Fe comes first and is the metal, it will have a positive charge (cation). Likewise, Cl comes second and will have a negative charge (anion). Criss Cross and add positive and negative sign. Iron is +3 so we give roman numeral of III. This is iron (III) chloride. iron (III) chloride
Criss Cross: Difficult PbS PbS Pb1 S1 Pb+1x2S-1x2 Pb+2 S-2 More electronegative species will carry negative charge meaning it will gain the electrons. Sulfur is in Group 6A and wants to get to 8. How many electrons will it gain? 2e Criss cross does not work. We already know sulfur is -2. But criss crossing gets us -1. To get from -1 to -2, we have to multiply by common factor of 2. We now know Pb is +2 so we give roman numeral of II. This is lead (II) sulfide. lead (II) sulfide
Criss Cross: Difficult PbS2 PbS2 Pb2 S1 Pb+2x2S-1x2 Pb+4 S-2 More electronegative species will carry negative charge meaning it will gain the electrons. Sulfur is in Group 6A and wants to get to 8. How many electrons will it gain? 2e Criss cross does not work. We already know sulfur is -2. But criss crossing gets us -1. To get from -1 to -2, we have to multiply by common factor of 2. We now know Pb is +4 so we give roman numeral of IV. This is lead (IV) sulfide. lead (IV) sulfide
Naming Binary Compounds CaCl2 CrBr3 C2S4 NO2 Fe3N2 Na3P
How do charges help you decide subscripts? Look up the charges for each element (or polyatomic ion). Determine the least common multiple between the two charges. The factor each charge needs to be multiplied by to give the least common multiple will be the subscript for that element.
Criss Cross lead (II) sulfide Pb+2 S-2 Pb+2 S-2 Pb2S2 More electronegative species will carry negative charge meaning it will gain the electrons. Sulfur is in Group 6A and wants to get to 8. How many electrons will it gain? 2e Drop the positive or negative sign when you criss cross. What is the least common multiple? 2 This can be simplified PbS
Criss Cross lead (IV) sulfide Pb+4 S-2 Pb+4 S-2 Pb2S4 More electronegative species will carry negative charge meaning it will gain the electrons. Sulfur is in Group 6A and wants to get to 8. How many electrons will it gain? 2e What is the least common multiple? 2 This can be simplified PbS2
Criss Cross iron (II) chloride Fe+2 Cl-1 Fe+2 Cl-1 Fe1Cl2 More electronegative species will carry negative charge meaning it will gain the electrons. Chlorine is in Group 7A and wants to get to 8. How many electrons will it gain? 1e What is the least common multiple? None This is already simplified FeCl2
Criss Cross iron (III) chloride Fe+3 Cl-1 Fe+3 Cl-1 Fe1Cl3 More electronegative species will carry negative charge meaning it will gain the electrons. Chlorine is in Group 7A and wants to get to 8. How many electrons will it gain? 1e What is the least common multiple? None This is already simplified FeCl3
Finding Formulas copper(II) chloride aluminum nitride calcium bromide iron(III) sulfide carbon disulfide dibromine monoxide barium fluoride disilicon tetrachloride
Polyatomic Ions Ions composed of more than one atom. You will need to learn their names, formulas and charges.
Polyatomic Ions Polyatomic means composed of more than 1 atom. A big exception to the metal with a nonmetal rule for ionic compounds comes from NH4+in for example NH4Cl. Here everything is nonmetal but still ionic b/c of charges (ions)
Naming Ionic Compounds Polyatomic Ionic Compounds sodium hydroxide: Na+ OH– NaOH magnesium carbonate: Mg2+ CO32– MgCO3 sodium carbonate: Na+ CO32– Na2CO3 iron(II) hydroxide: Fe2+ OH– Fe(OH)2
Naming Compounds with Polyatomics Ca(NO3)2 CrPO4 Na2CO3 (NH4)3PO4 Fe3(SO4)2 Li3ClO3 Easiest way to identify a polyatomic containing compound is to look at the compound and see if it consists of more than 2 elements. If it does, it is polyatomic. Also, most of the polyatomic ions contain oxygen. KEEP POLYATOMIC IONS GROUPED FOR CRISS CROSSING.
Finding Formulas with Polyatomics copper(II) chlorate aluminum nitrate calcium phosphate iron(III) sulfate sodium acetate barium hydroxide strontium carbonate
Day 1 Nitrate NO3-1 Chlorate ClO3-1 Bromate BrO3-1 Iodate IO3-1 Carbonate CO3-2 Sulfate SO4-2 Phosphate PO4-3
Day 2 Nitrite NO2-1 Chlorite ClO2-1 Sulfite SO3-2 Hydrogen Phosphate HPO4-2 Dihydrogen Phosphate H2PO4-1 Hydrogen Carbonate HCO3-1 (bicarbonate) Hydrogen Sulfate HSO4-1
Day 3 Permanganate MnO4-1 Hypochlorite ClO-1 Perchlorate ClO4-1 Periodate IO4-1 Acetate C2H3O2-1 Chromate CrO4-2 Dichromate Cr2O7-2
Day 4 Peroxide O2-2 Cyanide CN-1 Hydroxide OH-1 Arsenate AsO4-3 Oxalate C2O4-2 Ammonium NH4+1
Symbols seen in a reaction. (g) gaseous (s) Solid (l) liquid (aq) aqueous (dissolved in water) heat applied
Parts of a reaction Reactants: beginning chemicals in a reaction. Products: chemicals formed from a reaction. Coefficients: numbers in front of chemical symbols indicating the number of moles of each chemical involved in the reaction.
Writing a reaction. Make sure all the subscripts are correct (check charges, or use prefixes when going from words to formulas) Make sure you have the same number of each element on both sides of the reaction. Coefficients and subscripts multiply to determine the amount of each element. Use coefficients to balance reactions.
Example 1 Write the formulas for each reaction and balance: • Aluminum chloride + sodium carbonate aluminum carbonate + sodium chloride • Iron(II)oxide + potassium iodide iron(II)iodide + potassium oxide • Calcium phosphate + chromium(III)nitride calcium nitride + chromium phosphate
Types of Reactions * Synthesis, Composition, Combination *Single Replacement, Single Displacement *Double Replacement, Double Displacement *Decomposition *Combustion
Diatomic elements H,O,N,Cl,Br,I,F *Everything else can be written monatomically. Ex: Iron can be written as Fe (this is elemental form)
Synthesis (S) A + B AB H2 + O2 Sodium + chlorine Zinc + oxygen
Synthesis (S) A + B AB 2H2 + O2 2H2O Sodium + chlorine 2Na + Cl2 2NaCl Zinc + oxygen 2Zn + O2 2ZnO
Single Replacement A + BC AC + B Zinc + hydrochloric acid Sodium + Aluminum nitrate Calcium + water *Group 1A or 2A metals reacting with water, write water as HOH
Single Replacement A + BC AC + B Zinc + hydrochloric acid Zn + 2HCl ZnCl2 + H2 Sodium + Aluminum nitrate 3Na + Al(NO3)3 3NaNO3 + Al Calcium + water Ca + 2HOH Ca(OH)2 + H2 *Group 1A or 2A metals reacting with water, write water as HOH
Double Replacement AB + CD AD + CB Silver(I)nitrate + Calcium chloride Barium hydroxide + hydrofluoric acid Aluminum oxide + magnesium iodide
Double Replacement AB + CD AD + CB Silver(I)nitrate + Calcium chloride 2AgNO3 + CaCl2 2AgCl + Ca(NO3)2 Barium hydroxide + hydrofluoric acid Ba(OH)2 + 2HF BaF2 + 2HOH Aluminum oxide + magnesium iodide Al2O3 + 3MgI2 2AlI3 + 3MgO
Decomposition: AB A + B Mercury(II)oxide Aluminum chloride
Decomposition: AB A + B Mercury(II)oxide 2HgO 2Hg + O2 Aluminum chloride 2AlCl3 2Al + 3Cl2