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. EXCEPTION: When combined with a metal, it is -1. 6. Oxygen is usually -2 in compounds EXCEPTIONS: 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 numbers in a neutral compound must be zero. 8. The sum of the oxidation numbers in a polyatomic ion must equal the overall charge.

1) MnO4-1 2) Zn(NO2)2 3) Mn(NO3)3 4) NH4OH 5) Cu2S 6) PbO2 Assign oxidation states to each atom in the following: 1) MnO4-1 2) Zn(NO2)2 3) Mn(NO3)3 4) NH4OH 5) Cu2S 6) PbO2

Naming Binary Ionic Compounds Binary Ionic: 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

Naming Ternary Ionic Compounds 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) Check- Always assign oxidation state to first non- metal ***also note that a prefix system may be used …

The Prefix System ***ONLY for NM to NM Mono = one Di = two Tri = three Tetra = four Penta = five Hexa = six Hepta = seven Octa = eight Nona = nine Deca = ten

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)

Writing Formulas for Ionic Compounds 1) Determine charges on cation (+) and anion (-) 2) Determine ratio of ions that makes compound neutral 3) Write ratio as subscripts (do not write subscripts of “1”) Use parentheses around polyatomic ions ONLY if there is more than one

Helpful Tips for Formula Writing “-ide” ending usually indicates a binary compound (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 tend to behave like non-metals and therefore will have prefixes

Naming Acids Acids are a 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

Hydrated Crystals

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

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

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

Practice- In Notebooks Write the names for the following acids: HF (aq) HSCN (aq) HClO2 (aq) H2S (aq) H2SO3 (aq) H2CO3 (aq) HC2H3O2 (aq)

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

Write the names of the following ionic compounds: 1) NaBr 2) Cu2S 3) Znl2 4) KCl 5) MnO2 6) Fe2O3 7) Mg3P2

Write the names of the following ionic compounds: 1) CuSO4 2) AgClO3 3) Zn(NO2)2 4) NaC2H3O2 5) Fe(OH)3 6) NH4OH