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.

Ionic Bonds In the formation of sodium chloride, one electron is transferred from the sodium atom to a chlorine atom. 11 protons 11 electrons 17 protons 17 electrons Na+ + Cl– Na + Cl2 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 low IONIZATION ENERGY They tend to lose one or more electrons. Nonmetals tend to have high ELECTRON 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

Flow Chart to follow

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. PCl3 b. N2O3 c. 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 Name Criss 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 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 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 Pb1 S1 Pb+1x2 S-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 Pb2 S1 Pb+2x2 S-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

Determining Formulas from Names

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: Going from Name to Formula

Pb+2 S-2 Pb2S2 PbS Criss Cross lead (II) sulfide 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

Pb+4 S-2 Pb2S4 PbS2 Criss Cross lead (IV) sulfide 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

Fe+2 Cl-1 Fe1Cl2 FeCl2 Criss Cross iron (II) chloride 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

Fe+3 Cl-1 Fe1Cl3 FeCl3 Criss Cross iron (III) chloride 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)

Polyatomic 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

Chemical Reactions

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

Decomposition of polyatomic ions Metal chlorate  metal chloride + O2 Metal carbonate  metal oxide + CO2 Metal hydroxide  metal oxide + H2O

Metal Chlorates Potassium chlorate  Calcium chlorate  Iron(III)chlorate 

Metal Chlorates Potassium chlorate  2KClO3  2KCl + 3O2 Calcium chlorate  Ca(ClO3)2  CaCl2 + 3O2 Iron(III)chlorate  Fe(ClO3)3  FeCl3 + 4.5O2 OR 2Fe(ClO3)3  2FeCl3 + 9O2

Metal Carbonates Calcium carbonate  Aluminum carbonate  Copper(I)carbonate 

Metal Carbonates Calcium carbonate  CaCO3  CaO + CO2 Aluminum carbonate  Al2(CO3)3  Al2O3 + 3CO2 Copper(I)carbonate  Cu2CO3  Cu2O + CO2

Metal Hydroxides Sodium hydroxide  Chromium(III)hydroxide  Magnesium hydroxide 

Metal Hydroxides Sodium hydroxide  2NaOH  Na2O + H2O Chromium(III)hydroxide  2Cr(OH)3  Cr2O3 + 3H2O Magnesium hydroxide  Mg(OH)2  MgO + H2O

Combustion CxHy + O2  CO2 + H2O CxHyOz + O2 To balance, start with hydrogen, then carbon, end with oxygen. C8H18 + O2  C2H6O + O2 

Combustion To balance, start with hydrogen, then carbon, end with oxygen. C8H18 + 12.5O2  8CO2 + 9H2O OR 2C8H18 + 25O2  16CO2 + 18H2O C2H6O + 3O2  2CO2 + 3H2O