Cpt 7 Chemical formulas

Guided Reading, pages 164-170 What is a chemical symbol? Why do they use them? What is the format for a chemical symbol? What do you call an atom that has become electrically charged? There are two types of ions: cations and anions. What is the difference between them? Which type looses electrons? Which type gains electrons? What is formed when an anion bonds with a cation? What is the difference between monatomic and polyatomic ions. Give examples. What is the difference between chemical formulas and structural formulas? Give examples. What is a diatomic molecule? List the 7 diatomic gases. Define oxidation number. What is the difference between ionic compounds and molecules? Explain in detail with examples.

Positive Ions (Cations) Names, Formulas and Charges of Common Ions Oxidation numbers of Common Monatomic and Polyatomic Ions – cations (positive ions) Positive Ions (Cations) 1+ 2+ 3+ 4+ Ammonium NH4+ Barium Ba2+ Aluminum Al3+ Tin(IV) Sn4+ Cesium Cs+ Calcium Ca2+ Antimony(III) Sb3+ (Stannic) Copper(I) Cu+ Chromium Cr2+ Arsenic(III) As3+ Lead(IV) Pb4+ (Cuprous) Cobalt Co2+ Bismuth(III) Bi3+ (Plumbic) Francium Fr+ Copper(II) Cu2+ Boron B3+ Manganese(IV) Mn4+ Gold Au+ (Cupric) Chromium(III) Cr3+ Hydrogen H+ Iron(II) Fe2+ Cobalt(III) Co3+ Lithium Li+ (Ferrous) Iron(III) Fe3+ Potassium K+ Lead(II) Pb2+ (Ferric) Rubidium Rb+ (Plumbus) Titanium(III) Ti3+ Silver Ag+ Magnesium Mg2+ Manganese(II) Mn2+ Mercury(I) Hg22+ 5+ (Mercurous) Antimony(V) Sb5+ Mercury(II) Hg2+ Arsenic(V) As5+ (Mercuric) Bismuth(V) Bi5+ Nickel(II) Ni2+ Tin(II) Sn2+ (Stannous) Zinc Zn2+

Negative Ions (Anions) Rules for Writing Chemical Formulae Oxidation numbers of Common Monatomic and Polyatomic Ions – Anions (a negative ion) Negative Ions (Anions) 1- 2- 3- 4- Acetate C2H3O2- Carbonate CO32- Arsenate AsO43- Ferrocyanide Fe(CN)64- Bromate BrO3- Chromate CrO42- Borate BO33- (Hexacyanoferrate(II)) Bromide Br- Dichromate Cr2O72- Nitride N3- Silicate SiO44- Chlorate ClO3- Hydrogen-phosphate HPO42- Phosphate PO43- Chloride Cl- (Biphosphate) Phosphite PO33- Cyanide ClO2- Oxalate C2O42- Phosphide P43- Dihydrogen Oxide O2- phosphate H2PO4- Peroxide O22- Fluoride F- Sulfate SO42- Rules for Writing Chemical Formulae Hydride H- Sulfide S2- RULE 1: The resulting formula for a compound must have a total net charge of zero (0). RULE 2: Write the positive ion first and cross the valences. RULE 3: Do not cross any signs, and don’t write any signs in the formula. RULE 4: Don’t cross any ones. RULE 5: If both valences are the same, don’t cross them. RULE 6: More than one atom, more than one time, use parentheses. RULE 7: If the final answer has subscripts that can be reduced, they must be reduced. Bicarbonate HCO3- Sulfite SO32- Hydrogen Thiosulfate S2O32- oxalate HC2O4- sulfate HSO4- sulfide HS- Some Common Acids sulfite HSO3- Acetic HC2H3O2 Hydroxide Carbonic H2CO3 Hypochlorite ClO- Hydrochloric HCl Iodide I- Hydrobromic HBr Nitrate NO3- Hydrofluoric HF Nitrite NO2- Nitric HNO3 Perchlorate ClO4- Phosphoric H3PO4 Permanganate MnO4- Sulfuric H2SO4 Thiocyanate SCN-

Formulas and Names of Binary Metal-Nonmetal Compounds The name of the metal is first (ie: NaCl, sodium chloride) The name of the nonmetal has -ide added (ie: NaCl sodium chloride) IF the metal has more than one possible charge You must indicate which ion using the charge in roman numerals (ie: FeCl2 Iron (II) chloride). More examples showing the two different systems: Compound Name FeF2 iron (II) fluoride FeF3 iron (III)fluoride Hg2Br2 mercury (I) bromide HgBr2 mercury (II) bromide

Formulas and Names of Binary Nonmetal-Nonmetal Compounds Systematic Nomenclature: For names start with element to the left side on the periodic table add -ide to the second element use Greek prefixes for number of atoms: mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca Example: CO carbon monoxide CO2 carbon dioxide N2O5 dinitrogen pentoxide Formula Systematic Name NO nitrogen monoxide N2O dinitrogen monoxide NO2 nitrogen dioxide N2O5 dinitrogen pentoxide N2O3 dinitrogen trioxide

Polyatomic Compounds. Naming compounds with polyatomic ions Positive charge species on left (using common name) Negative charge species on right (using name of polyatomic ion) In the formula: use parentheses if a subscript is needed Formula Ions Name BaSO4 Ba2+ and SO42- barium sulfate Ca(NO3)2 Ca+2 and NO31- calcium nitrate Ca(NO2)2 Ca+2 and NO21- calcium nitrite Fe(NO3)2 Fe2+ and NO31- iron (II) nitrate

Acids Have their own set of rules (we do them in Cpt 23). For now know: HCl Hydrochloric Acid HNO3 Nitric Acid H2SO4 Sulfuric Acid

Naming Organic Compounds carbon compounds that exist as molecules We will focus on Hydrocarbons - Simplest group of organic compounds made of only H and C. Carbon atoms can link in chains,branches, or rings. Eg:

Rules for naming Hydrocarbons: Count carbon atoms shown and find the prefix for it. 1 C = meth 6 = hex 2 = eth 7 = hept 3 = prop 8 = oct 4 = but 9 = non 5 = pent 10 = dec Add a suffix to show how the carbon atoms link to each other. For now we only use –ane.

Methane: CH4 H H C H H Ethane C2H6 - C – C – # H = #C x 2 + 2

More examples C C is cyclobutane If it’s a cycloalkane: #H = #C x 2 Do Page 178 # 13 and 14.

Molecular and Empirical Formulas Molecular Formulas- used for compounds that exist as molecules; Used for carbon compounds, 2 nonmetals together, or a nonmetal with Hydrogen shows the actual number of atoms of each element making up a molecule. (Often the subscripts are not in lowest terms). E.g. H20 and H2O2 and NO2 and C2H6 and CH4

Molecular and Empirical Formulas, continued Empirical Formulas – used to show most ionic compounds. Formula is given in the simplest ratio between the atoms present in the compound (this means subscripts are in lowest terms) e.g. Al2(SO4)3 BaCl2

What is the empirical formula for C2H8? A chemical formula is also called a formula unit. Coefficients – used to show the number of formula units that you want to represent 3 H2O means you want 3 formula units of water. Do page 180 #15-16