Chemical Names and Formulas Unit 5

Counting Atoms The subscript tells how many of that element is present. Eg: H2O2= 2 hydrogen, 2 oxygen If there is no subscript next to the symbol, it counts as “1”. Eg: NaCl = 1 sodium & 1 chlorine

Counting Atoms If the subscripted number is outside of the parenthesis, it is distributed to all elements within the parenthesis. Eg: Ca(NO3)2 = NO3 x 2. A preceeding coefficient is multiplied to all atoms in the compound. Eg: 2NaCl = 2 sodium & 2 chlorine

Counting Atoms Calcium Carbonate: CaCO3. Ca = Calcium = 1 C = Carbon = Oxygen = 3 5 Total atoms =

Counting Atoms Magnesium Hydroxide: Mg(OH)2. Mg = Magnesium = 1 H = Hydrogen = 2 O = Oxygen = 2 5 Total atoms =

Counting Atoms Acetic Acid: 2HC2H3O2. Hydrogen = 2 + 6 = 8 C = Carbon = 4 O = Oxygen = 4 16 Total atoms = Now complete the Counting Atoms review worksheet.

IMPORTANT: ALL COMPOUNDS ARE NEUTRAL!!! Chemical Formulas The simplest compounds contain 2 elements and are called Binary. In ionic binary compounds, a cation and an anion join together to form a neutral compound. Ionic compounds are made from a metal and a non-metal. IMPORTANT: ALL COMPOUNDS ARE NEUTRAL!!! Ionic Compound Cation + Anion =

Chemical Formulas Potassium Bromide = KBr Calcium Bromide = CaBr2 Lithium Fluoride = LiF Lithium Oxide = Li2O Note that the subscript has nothing to do with the name of the ionic compound.

Chemical Names Example: LiF The element with the positive charge, cation (the metal) is written first. This element is given its usual name, in this case, Lithium. The second element is the anion. It’s name will be changed to end in “-ide”. Fluorine is changed to Fluoride. The compound’s name = Lithium Fluoride.

Chemical Formula for Potassium Bromide Write the two symbols for the ions in the compounds, placing the symbol for the cation first. +1 -1 K Br KBr Balanced! Determine the charge of each ion from the oxidation state on the periodic table. If the charges are equal, drop them and write the formula.

Calcium Bromide If the charges are not equal, “lasso” the number only (not the sign) to write the formula. 1 + 2 2 - 1 Ca Br CaBr2 NOT Balanced! After seeing more examples, complete practice problems 1-10 on your worksheet.

Transition Elements and Roman Numerals Some metals can form more than one type of ion and therefore, have more than one possible charge. To tell which charge is used, the chemical name contains a Roman numeral. The Roman numeral tells the charge of the cation.

Transition Elements and Roman Numerals WARNING Roman numerals are NEVER used in the chemical formula!!

Rules to Write a Chemical Formula when Roman Numerals are Present To write the chemical formula for Iron (III) Sulfide: Write the two symbols for the ions in the compounds, placing the symbol for the cation first. Get the charge of the metal from the Roman numeral in ( ) after the metal and look up the anion’s charge. - 2 2 Fe2S3 + 3 3 Fe S

Rules to Write a Chemical Name when Roman Numerals are Needed If the metal has more than one oxidation state, the chemical name will contain a Roman numeral. Oxygen has a charge of -2 and there are 3 for a total charge of -6. Mn must have a charge of +6 to neutralize the -6 charge. Mn can have a charge of +7, 6, 4, 2 or 3 Now write the chemical name using a roman numeral to represent the charge of the Manganese. Start with the anion to determine its overall negative charge. You CANNOT lasso up to determine the Roman numeral. Manganese (VI) Oxide MnO3

Let’s Try Again Fe2O3 Write the chemical name of Fe2O3. Rust The 2 Fe ions must have an overall charge of +6. So 6/2 = +3. Fe can have a charge of +2 or 3 Oxygen has a charge of -2 and there are 3 for a total charge of -6. Rust Fe2O3 Iron (III) Oxide Now write the chemical name. Now do part C of your worksheet.

Polyatomic Ions in Names The cation keeps its name. CaCO3 Carbonate Calcium Made of more than one element so it is a polyatomic ion. The polyatomic ion also keeps its name, even though it is an anion.

Polyatomic Ions in Formulas Barium Phosphate We recognize Phosphate as a polyatomic ion because it ends in “ate”. Get the charge of the polyatomic ion from the chart. Use the periodic table for the charge on your element.

Barium Phosphate Ba PO4 Let’s Lasso! Add each ion’s charge. NO!! Write the chemical symbols. Are the charges balanced? - 3 3 + 2 2 Ba PO4 We have 2 “PO4” ions so we need parentheses to separate the ion from the extra subscript. Ba3(PO4)2

Let’s Try Again Mg OH Write the formula for Magnesium Hydroxide. + 2 2 - 1 1 Mg OH We have 2 “OH” ions so we need parentheses to separate the ion from the subscript. Mg(OH)2 Now do part D of your worksheet.

Covalent Compounds Covalent compounds are made from 2 non-metals and are binary. Since there are no ions involved, we don’t look at charges. The subscript to the right of the element tells the prefix to use for that element. SO2 = Sulfur Dioxide

Covalent Compound Prefixes Mono = one Di = two Tri = three Tetra = four Penta = five Hexa = six Hepta = seven Octa = eight Nona = nine Deca = ten Triangle Hexagon

Some Covalent Compounds NF3 nitrogen trifluoride N2Cl4 dinitrogen tetrachloride NO2 nitrogen dioxide TOXIC! N2O dinitrogen monoxide Laughing Gas Now do part E of your worksheet.

Naming Acids Acids = compounds that give off hydrogen ions when dissolved in water. Acids begin with H. Acids will always have some H next to an anion. The anion determines the name.

Binary Acids Binary Acids contain only 2 elements, the cation being hydrogen. Add the prefix hydro-, take the anion name and change the suffix -ide to –ic. HCl(aq) Hydrochloric Acid HF(aq) Hydrofluoric Acid HI(aq) Hydroiodic Acid

Binary Acids Exceptions: HCN = Hydrocyanic Acid CN = Cyanide HN3 = Hydroazoic Acid azo = Nitrogen

Oxyacids Ternary Acids contain 3 elements, hydrogen, oxygen and one other element (a polyatomic ion). The suffix is determined by the number of oxygens. If the anion ends in -ate, change the suffix to –ic acid. HNO3 = Hydrogen & Nitrate = Nitric Acid

More Oxyacids H2SO4 = Hydrogen & Sulfate = Sulfuric Acid HClO3 = Hydrogen & Chlorate = Chloric Acid

More Oxyacids If the anion has one less oxygen & ends in -ite, change the suffix to –ous acid. Hydrogen & Nitrite = HNO2 = Nitrous Acid H2SO3 = Hydrogen & Sulfite = Sulfurous Acid HClO2 = Hydrogen & Chlorite = Chlorous Acid

Name these Acids HF H3P H3PO4 H3PO3 HCN H2CrO4 Hydrofluoric Acid Hydrophosphic Acid Phosphoric Acid Phosphorous Acid Hydrocyanic Acid Chromic Acid

Oxyacids If a third acid is formed with fewer oxygens than -ite, it is given the prefix hypo- and the suffix –ous. E.g. HClO = Hydrogen & hypochlorite = Hypochlorous Acid If it has one more oxygen than -ate, it is given the prefix per- and the suffix –ic. E.g. HClO4 = hydrogen & perchlorate = Perchloric Acid.

Writing Formulas for Acids Hydrogen will always be first. The name tells you the anion. Make sure the molecule is neutral. If the name starts with the prefix hydro- and ends with -ic, there is no oxygen in the formula. If there is no prefix, the suffix –ate comes from –ic and –ite comes from –ous.

Write Formulas for these Acids hydroiodic acid acetic acid carbonic acid phosphorous acid hydrobromic acid HI HC2H3O2 H2CO3 H3PO3 HBr

Naming Organic Compounds Hydrocarbons are compounds made of only carbon and hydrogen linked in long chains. Alkanes – have single bonded carbons so they are saturated.

Naming Organic Compounds Alkenes – have double bonded carbons so they are unsaturated. Alkynes – have triple bonded carbons We’ll work with alkanes so hydrocarbons will have the suffix –ane.

Organic Stems 1 carbon = meth- 6 carbons = hex- 2 carbons = eth- 7 carbons = hept- 3 carbons = prop- 8 carbons = oct- 4 carbons = but- 9 carbons = non- 5 carbons = pent- 10 carbons = dec-

Organic Compounds If the atoms are linked in a ring rather than in a chain, the prefix cyclo- is added. Hexane in a chain CH3-CH2- CH2- CH2- CH2- CH3. Cyclohexane has 6 carbons in a ring. Each point represents a carbon.

Organic Compounds If the chain is straight: CnH2n+2 n=#carbons E.g. C3H(2×3)+2 = C3H8 = Propane CH3-CH2-CH3 If the chain is cyclic: CnH2n E.g. C3H6 = cyclopropane