Unit 5: Naming and Formula Writing

What is a polyatomic ion? (Table E) Tightly bound atoms that behave as a unit and carry a charge Ex: SO42- , HPO42- The names of most polyatomic ions end in “–ite” or “–ate”

5 important PAIs have different endings: H3O+ = hydronium NH4+ = ammonium CN- = cyanide OH- = hydroxide O22- = peroxide

“ites” vs. “ates” Sulfite: SO32- Nitrite: NO2- Chlorite: ClO2- ONE LESS OXYGEN ATOM Sulfate: SO42- Nitrate: NO3- Chlorate: ClO3- ONE MORE OXYGEN ATOM

Oxidation Number (State) identifies how many electrons are either lost or gained by an atom or ion during a chemical reaction

Rules for assigning oxidation numbers: An element by itself has an oxidation number of zero. Ions have an oxidation # equal to their charge. In compounds, Group 1 metals are +1 and Group 2 metals are +2. Fluorine always has an oxidation # of -1 in compounds.

Rules for assigning oxidation numbers: 5. Hydrogen is +1 in compounds. EXCEPT: When combined with a metal, it is -1. 6. Oxygen is usually -2 in compounds EXCEPT: When combined with fluorine, oxygen is a +2. Oxygen is -1 in the peroxide ion (Table E) Found in H2O2 or Group 1/Group 2 metal with peroxide 7. The sum of the oxidation #s in a neutral compound must be zero. 8. The sum of the oxidation #s in a polyatomic ion must equal the overall charge.

1) MnO4-1 2) PbO2 3) Zn(NO2)2 4) NiF3 5) Mn(NO3)3 6) SO32- Assign oxidation states to each atom in the following: 1) MnO4-1 2) PbO2 3) Zn(NO2)2 4) NiF3 5) Mn(NO3)3 6) SO32- 7) NH4OH 8) LiH 9) CaCO3 10) MgO2 11) Cu2S

Use the rule: NAME, NAME, CHECK!  IUPAC Naming System Binary Ionic Compounds: Two elements (1 metal and 1 non-metal) Use the rule: NAME, NAME, CHECK! 1) Name metal (full name of metal) 2) Name non-metal (change ending to –ide) 3) Check to see if the metal has one ox. state or more than one ox. state If only one ox. state: no Roman Numerals If more than one ox. state: assign proper charge to metal and put in parentheses as a Roman Numeral

Ternary Ionic: Metal with more than one non-metal (will contain a PAI from Table E) 1) Name metal (full name) 2) Name polyatomic (keep ending on Table E!) 3) Check- (same as binary ionic compounds) ***For cmpds with two PAIs, simply name the first and second PAIs in order (ex. NH4OH) ***still considered ionic even though there is no metal***

Naming Binary Covalent Compounds Binary Covalent: Two non-metals 1) Name non-metal first (full name) 2) Name non-metal second (change ending to –ide) 3) ALWAYS assign oxidation state to first non-metal

Formula Writing 1) Determine ratio that makes compound neutral 2) Write ratio as subscripts (do not write subscripts of “1”) Use parentheses around PAIs ONLY if there is more than one

Helpful Tips: “-ide” ending usually indicates a binary cmpd (except if there is a polyatomic like hydroxide, peroxide) “-ate” and “-ite” endings indicate a PAI on Table E

Writing Formulas for Covalent Compounds Prefix System: Convert prefixes into subscripts Do not write a subscript of “1” Roman Numeral System (Stock System): Use roman numerals to determine proper ratio of NM to NM **Some metalloids behave like non- metals and therefore will have prefixes (ex. Si)

The Prefix System: Another naming system for COVALENT only 1 = mono 2 = di 3 = tri 4 = tetra 5 = penta 6 = hexa 7 = hepta 8 = octa 9 = nona 10 = deca

Using Prefixes… Name first element. Only use prefix if there is more than one. ALWAYS use a prefix for second element and change ending to –ide. If prefix ends in an “o” or an “a”, these letters are dropped for oxygen (ex. monoxide, NOT monooxide)

Hydrated Crystals

Hydrated Crystals Ionic compounds in which the ions are surrounded by water molecules Also called hydrates Example: CaCl2 ● 2H2O Note: the dot does NOT represent multiplication! Naming: calcium chloride dihydrate

Naming hydrates calcium chloride dihydrate Name the ionic compound Add prefix for the # of water molecules followed by “hydrate” Ex) CaCl2 ● 2H2O calcium chloride dihydrate

Percent Composition by Mass

Percent Composition by Mass Ex #2) What is the percent by mass of water in CaSO4●2H2O?

Data Table: Heating of CaSO4 •2H2O Mass of crucible 15.03 g Mass of crucible and hydrate 17.90 g Mass after first heating 17.25 g Mass after second heating 17.22 g Mass after third heating 17. 22 g

Naming Acids Acids: group of compounds that produce hydrogen ions (H+) when dissolved in water H+ ions are also called hydronium ions (H3O+) Chemical formula of acids is generally HnX (aq) n = number of hydrogen ions X = anion

Naming Binary Acids If the acid is binary (H and one other element), use the template: hydro_______ic acid Ex. HCl HI H2S Root of anion

Naming Ternary Acids 2) If the acid contains a polyatomic ion, change ending of PAI using the rule: ate  ic ite  ous Ex. H2SO4 H2SO3 HNO3 HNO2

Writing Formulas for Acids Use the rules for writing the names of acids in reverse Be sure that the charges cancel!! Ex. hydrobromic acid Ex. Phosphoric acid Ex. hydroiodic acid Ex. Hypochlorous acid Ex. Sulfurous acid Ex. Carbonic acid

Molecular vs. Empirical Formulas Molecular Formula: The actual number of atoms bonded together in a molecule (NM to NM) Ex: C6H12O6 Empirical Formula: The smallest whole number ratio of atoms in a molecule Ex: CH2O ** Ionic cmpds are ALWAYS written as an empirical formula **Covalent cmpds (molecules) may be in the empirical or molecular form