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A. Definition • Remember, a compound consists of 2 or more elements chemically bonded together. It is always neutral. EX: H20, NaCl, Sb3(PO4)5 • There are two main ways to name chemical compounds. However, before you can even think about naming the compound you must decide what kind of compound you have. Do you have a covalent or ionic compound? We already learned this using the terms molecule and formula unit. • Most formulas are written with the elements listed from left to right on the periodic table What do you remember about the difference between a molecule and a formula unit? B. Types of Compounds 2 types of chemical compounds Samples Ionic Compounds Molecular Compounds • Rock salt (NaCl) • Calcium Carbonate (CaCO3) • Potassium Nitrate (KNO3 ) • Sugar (C12H22O11) • Methane gas (CH4) 1. Ionic Compound: Ionic Compound: a compound that is formed by ions of opposite charges. It is held together by an ionic (transfer electrons) bond and usually contains a metal and nonmetal. EX: NaCl, Sb3(PO4)5 smallest unit is called a formula unit 2. Molecular or Covalent Compound: • Molecular or Covalent compound: consists of only nonmetal atoms and is held together by covalent (share electrons) bonds EX: H20, C8H18 smallest unit is called a molecule How can I tell!? • Look for a metal. • If there’s a metal, it’s an ionic compound Practice 1. Determine whether the following are ionic or molecular covalent compounds a. N2O5 molecular b. PbNO PbNO55 ionic c. KF ionic e. PCl3 molecular d. AgCl ionic Acids: have a formula that starts with hydrogen You need to know the names and formulas for the following acids: Acid Name Formula hydrochloric acid HCl nitric acid HNO3 sulfuric acid H2SO4 phosphoric acid H3PO4 Note: all acids start with “H” in their chemical formulas and include the word “acid” in their names. II. Molecular Compounds (aka Covalent Compounds aka Molecules) Molecular Compounds = share electrons HO H H2O A. Binary Molecular Compounds • Molecular compounds DO NOT contain a metal atom • Molecular compound contain covalent bonds • We use prefixes to name molecular, ONLY MOLECULAR, compounds How do I distinguish between the bikes? unicycle bicycle tricycle We use prefixes to help distinguish molecular compounds. Prefix Number of Atoms mono 1 di 2 tri 3 tetra 4 penta 5 hexa 6 hepta 7 octa 8 nona deca 9 10 Why have prefixes? Nitrogen bonds to Oxygen in more than one way Ex: N2O, NO2, N2O2, N2O5 Examples: Formula: CO Name: carbon monoxide Formula: N2O Name: dinitrogen monoxide a. Naming binary molecular compounds: FIRST ELEMENT IN THE FORMULA – – keeps its full elemental name Add prefixes to signify the number of that specific kind of atom ONLY if there is more than one of the atoms. DON’T USE MONO ON THE FIRST SYMBOL SECOND ELEMENT IN THE FORMULA – – The second element name ALWAYS gets a prefix Keep the first syllable of the elemental name and change the suffix to “ide”. Practice: Formula: CO2 name: Carbon dioxide Formula: BF3 name: Boron trifluoride Formula: Cl2O name: Dichlorine monoxide Formula: P2S5 name: Diphosphorus pentasulfide B. Converting a name to a formula: • This exercise is very simple if you have memorized the element symbols and the prefixes. Just go backwards from what we just did. Examples: Formula: CCl4 Name: carbon tetrachloride. Formula: H2F Name: dihydrogen monofluoride Practice: Formula: H2O name: Dihydrogen monoxide Formula: NO5 name: Nitrogen pentoxide Formula: CF4 name: CarbonTetrafluoride Formula: SiO2 name: Silicon Dioxide 1+ 2+ 3+ 3- 2- 1- III. Naming ions 1. Monatomic Cations (+ ions) + One atom • Monatomic cations are named by writing the element’s name and then “ion” after it. • EX: Ca2+ Calcium ion Na+ Sodium ion a. Monatomic Cations (Transition + PASS + Z.A.C Elements ) • Most transition metals and “P.A.S.S” elements need Roman Numerals • Zinc (Zn), Silver (Ag), and Cadmium (Cd) are transition metals that DO NOT need Roman Numerals More than just “Iron ion” EX: Fe2+ Iron (II) ion Fe3+ Iron (III) ion Transition Metals need R.N. 1. Name these ions 4+ a. Pb Lead (IV) ion b. Pb2+ Lead (II) ion + c. Cu Copper (I) ion d. Cu2+ Copper (II) ion Examples 1. Name these ions 2+ a. Ca Calcium ion b. Na+ Sodium ion 4+ c. Fe Iron (IV) ion d. Zn2+ Zinc ion b. Monoatomic Anions (- ions) oMonatomic anions are named by changing the suffix to “ide” then adding “ion” after it. Cation or Anion? • Carbon can act as a cation (carbon ion) or as an anion (carbide ion). It just depends if it is in the beginning or the end of the compound’s formula • Hydrogen can also act as a cation (hydrogen) or as an anion (hydride). It just depends if it is in the beginning or the end of the compound’s formula. Don’t forget it is a non-metal. Complete the chart below Element Symbol Oxidation number Anion name Chlorine Cl- -1 Chloride ion Bromine Br- -1 Bromide ion Oxygen O2- -2 Oxide ion Sulfur S2- -2 Sulfide ion Phosphorus P3- -3 Nitrogen N3- -3 Phosphide ion Nitride ion Summary • List the elements that need Roman Numerals Transition metals, PASS elements (Pb, As, Sn, Sb) • List the transition metals that don’t need Roman Numerals Zn, Ag, Cd (Z.A.C elements) Anions: Change Suffix to -ide always 1+ 2+ 3+ 3- 2- 1- Zn2+ Ag+ Cd2+ Always need roman numerals Tips TM (Except ZAC) and PASS need Roman Numerals All metals are +; all non-metals are Anions end in -ide c. Polyatomic Cations • A polyatomic ion is a group of covalently bonded atoms that have an overall charge • Example NH4+ = ammonium. d. Polyatomic Anions • This means the anion is a COVALENTLY BONDED GROUP of atoms that have a – charge. They are EASY to deal with in naming and formula writing if you think of them as ONE UNIT that can not be altered in any way. Example: • Use the back of your periodic table to help you identify polyatomic anions Flip over your PT and let’s practice 1. Name these ions 2carbonate a. CO3 hydroxide b. OHnitrate c. NO3d. SO42sulfate phosphate e. PO43- IV. Binary Ionic Compounds a. Naming Binary Ionic Compounds • Ionic Compounds are made of a cation and anion pair. You already know how to name the ions. Just put the names together and leave off the word ion. Don’t forget Roman Numerals! Ionic Compounds = transfer of electrons + Na Cl NaCl Is formed - a. Naming Binary Ionic Compounds Formula Ions Ion names Compound name AlN Al3+ N3- Aluminum ion Nitride ion Aluminum nitride Na20 Na+ O2- Sodium ion Oxide ion Sodium oxide FeO Fe2+ O2- Iron (II) ion Oxide ion Iron (II) oxide Fe2O3 Fe3+ O2- Iron (III) ion Oxide ion Iron (III) oxide Ex. Name FeS NOT Iron Sulfide Iron (II) sulfide Remember to add a Roman Numeral for the cations that need one One trick to determine the Roman Numeral: 1. Add up your total negative charges 2. Divide the above number by the total number of metal ions 3. Change to a Roman Numeral 1. Add up your total negative charges 2. Divide the above number by the total number of metal ions 3. Change to a Roman Numeral Ex. Name FeS Total neg. charges: 22/1 (Fe) = 2 Iron (II) Sulfide Ex. Name Fe2O3 Total neg. charges: 66/2 (Fe) = 3 Iron (III) Oxide Practice 1. Name the following compounds a. ZnS Zinc sulfide b. K3N Potassium nitride c. BaO Barium oxide d. CaBr2 Calcium bromide e. SnF2 Tin (II) fluoride Practice 1. Name the following compounds f. CaO Calcium oxide g. AlF3 Aluminum fluoride h. CuI2 Copper (II) iodide i. Cu2Se Copper (I) Selenide j. Hg2O Mercury (I) Oxide b. Writing Formulas for Binary Ionic Compounds • Remember, a compound must be electrically neutral. Therefore, the total positive charge of the cation must equal the total negative charge of the anion. EX: calcium chloride Ca2+ ClTo make a neutral compound Ca2+ ClCl+2 -2 CaCl2 To write a formula for a binary ionic compound 1.Write the ions that are named in the compound showing oxidation numbers. 2. Determine how many of each ion you need to make a neutral compound. 3. To write the formula, list the metal symbol first and then the anion symbol, adding subscripts to indicate how many of each ion there is in the formula 4. Make sure the formula has the lowest whole number ratio. Note: you never write a 1 subscript; it is understood. EX: write the formula for aluminum fluoride Al+3 +3 FFF-3 Formula: AlF3 NOTE: You never include oxidation numbers in the chemical formula of a compound. Practice – only do a-c 1. Write chemical formulas for the following: a. strontium phosphide Sr3P2 b. potassium sulfide K2S c. iron (II) chloride FeCl2 The Criss-Cross Method • One easy way to figure out the formula of an ionic compound is to swap the oxidation number of each ion and use them as subscripts. (without the charge) • the formula must be in the lowest whole number ratio Just Watch!! sodium sulfide Na 1+ 1’s are understood S 2- Criss Cross Method Na2S Ex: Write the formula for iron (III) bromide Fe 3+ Br - Criss Cross Method FeBr3 Note: if both ox #’s are equal, you don’t need to use the crisscross method, just show 1 ion of each. Ex: Write the formula for magnesium sulfide Mg 2+ S 2- Magnesium Sulfide MgS Note: show the formula with the lowest whole number ratio. EX: write the formula for lead (IV) sulfide Pb 4+ S 2- Criss Cross Method Pb2S4 PbS2 Finish the Practice Box 1. Write chemical formulas for the following: d. antimony (V) nitride Sb3N5 e. iron (III) chloride FeCl3 f. Calcium bromide CaBr2 Naming • Same way as you already learned Formulas • Use subscripts to show how many of each ion you needed to make a neutral compound V. Ionic Compounds Containing Polyatomic Ions a. Writing Formulas for Polyatomic Compounds • Write formulas for polyatomic ions in the same way. Just remember the polyatomic ion acts as a whole unit and you need to use parentheses if you need more than 1 of them. • Note: You never change the • formula of a polyatomic ion! EX: calcium nitrate To make a neutral compound Ca2+ (NO3)(NO3)+2 -2 Ca(NO3)2 EX: Calcium Nitrate (using the criss cross method) 2+ Ca (NO3) - Practice Practice 1. Write formulas for the following compounds a. strontium sulfate SrSO4 b. lithium carbonate Li2CO3 c. potassium sulfate K2SO4 d. magnesium hydroxide Mg(OH)2 Practice Practice 1. Write formulas for the following compounds e. ammonium dichromate (NH4)2Cr2O7 f. potassium permanganate KMnO4 g. sodium hypochlorite NaClO h. barium sulfite BaSO3 b. Naming Polyatomic Compounds • It is important that you recognize the polyatomic • If there are more than 2 elements in the formula, then you know it contains a polyatomic. • Only one polyatomic is a cation, ammonium (NH4+) All the rest will come after the metal ion. • You name polyatomic compounds just like you would other ionic compounds -- you write the name of each ion. Note: most (not all) polyatomic compounds will end in -ate or -ite. Ex. Name ZnSO4 Zinc Sulfate Ex. Name NaOH Sodium hydroxide Practice 1. Name these compounds a. CaCO3 calcium carbonate b. KClO potassium hypochlorite c. KMnO4 potassium permanganate Practice 1. Name these compounds d. Al(OH)3 aluminum hydroxide e. Sn3(PO4)2 tin (II) phosphate f. Na2CrO4 sodium chromate