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Naming Compounds Writing Formulas
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There are more than 50 million named chemical substances Many have common names that we use everyday like sugar, table salt, borax, and sand They all have systematic names that make keep track of them easier and uniquely identify each one.
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Follow the Law of Definite Proportion. Have a constant composition. Same formula (atoms) every time Two Major Types of Compounds Ionic Covalent or Molecular
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Covalent Compounds Made of molecules Made by joining nonmetal atoms together into molecules Non-Metal Non-Metal Combinations Soft solids, liquids, and gases Carbon dioxide CO 2 Dihydrogen monoxide H 2 O
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Made of cations and anions Positive ion bonded to negative ion Metal Non-Metal Combinations The electrons lost by the cation are gained by the anion The cations and anions surround each other Smallest ratio of ions in an ionic compound is a FORMULA UNIT. All hard, brittle solids Calcium chloride CaCl 2
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K +1 Ca +2 Has lost two electrons Positive ions Formed by losing electrons More protons than electrons Metals usually Has lost one electron
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A negative ion Has gained electrons Non metals Charge is written as a superscript on the right. F -1 Has gained one electron O -2 Has gained two electrons
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Shows the kind and number of atoms in the smallest piece/ratio of a substance CO 2 C 6 H 12 O 6 AlBr 3
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The smallest whole number ratio of atoms in an ionic compound. Ions surround each other so you can’t say which is hooked to which
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The Stock (Roman numeral) System used for Ionic Compounds The Numerical Prefix System used for Covalent Compounds
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Write the name of the less electronegative element or polyatomic ion Write down the name of the other element or polyatomic ion Put a Roman numeral in parentheses after the first element name The Roman numeral is equal to the oxidation state (charge) of the first element
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Composed of 2 different elements Write down the name of the less electronegative element (metal) Write down the root of the other element then add ---ide to the end. Place the roman numeral in parentheses after the first element if needed Roman # equals the charge of the first element
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For Elements in Groups 1, 2,13-18 on the Periodic Table you can tell what kind of ion they will form from their location on the table Elements in the same group have similar properties Including the charge when they are ions
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+2 +1 +3-3-2
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We have to figure those out some other way. More on this later.
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We will use the systematic way Cation- if the charge is always the same just write the name of the metal (Gr. 1, 2, 13) Transition metals can have more than one type of charge Indicate the charge with a Roman numeral in parentheses How we determine this in a bit
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Na +1 Ca +2 Al +3 Fe +3 Fe +2 Pb +2 Li +1
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Potassium ion Magnesium ion Copper (II) ion Chromium (VI) ion Barium ion Mercury (II) ion
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Anions are always the same when it comes to charge Change the element ending to – ide F -1 fluoride S -2 sulfide P -3 phosphide Te -2 telluride
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Cl -1 N -3 Br -1 O -2 Ga +3
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Sulfide ion iodide ion phosphide ion Strontium ion
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Groups of atoms that stay together and have a charge You must memorize these or use an ion sheet Acetate C 2 H 3 O 2 -1 Nitrate NO 3 -1 Nitrite NO 2 -1 Hydroxide OH -1 Permanganate MnO 4 -1 Cyanide CN -1
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Sulfate SO 4 -2 Sulfite SO 3 -2 Carbonate CO 3 -2 Chromate CrO 4 -2 Dichromate Cr 2 O 7 -2 Phosphate PO 4 -3 Phosphite PO 3 -3 Ammonium NH 4 +1
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EndingFormulaName (from the element that is not oxygen) ChlorineFormula ---ideNo oxygenS-2SulfideChlorideCl -1 ---iteSome oxygen SO3-2SulfiteChloriteClO 2 -1 ---ateMore oxygen SO4-2SulfateChlorateClO 3 -1 Hypo--- --- ite Less oxygen HypochloriteClO -1 Per--- -----icMost oxygen PerchlorateClO 4 -1
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Binary Compounds 2 elements Metal nonmetal a cation and an anion + - To write the names just name the two ions.
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Easy with Representative elements Groups 1, 2, 13 Charge determined by location in table NaCl = Na + Cl - = sodium chloride MgBr 2 = Mg +2 Br - = magnesium bromide
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The problem comes with the transition metals and in other variable charged cations Elements not are not in groups 1, 2, or 13. Need to figure out their charges. How?
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The compound must be neutral Same number of + and – charges Look up the charge on the negative Calculate the total negative charge Must be equal to total positive charge Divide positive total by number of atoms Result is equal to charge on positive This is the Roman numeral
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Write the name of CuO Copper is not in gr 1, 2, or 13 so need a roman numeral O is -2 therefore Copper must be +2 so the roman numeral = 2 Name is Copper (II) chloride
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Name the following: CoCl 3
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Write the name of Cu 2 S
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Fe 2 O 3
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Write the names of the following KCl Na 3 N CrN Sc 3 P 2 PbO PbO 2 Na 2 Se
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Will have at least one polyatomic ions At least three elements Name the ions: Use a roman numeral if needed. NaNO 3 CaSO 4 CuSO 3 (NH 4 ) 2 O
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LiCN Fe(OH) 3 (NH 4 ) 2 CO 3 NiPO 4
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Things to remember: The charges in a compound have to add up to zero 1. Write down each ion with charges 2. Make the charges equal by adding subscripts 3. Put polyatomic ions in parentheses before using a subscript
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Write the formula for calcium chloride. Calcium is Ca +2 Chloride is Cl -1 Charge on compound must be 0. So 2 Cl -1 are needed to make the charge = to zero. CaCl 2 2 atoms of chlorine for every one atom of calcium
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Aluminum nitrate
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Lithium sulfide tin (II) oxide tin (IV) oxide Magnesium fluoride Copper (II) sulfate Iron (III) phosphide
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gallium nitrate Iron (III) sulfide Ammonium chloride ammonium sulfide barium nitrate
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If cation has a (Roman Numeral), the number is the charge of the positive ion If anions end in -ide they are probably off the periodic table (monoatomic) but can be cyanide, hydroxide If anion ends in -ate or -ite it is polyatomic
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Writing names and Formulas
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Nonmetal Nonmetal combinations smallest piece is a molecule Also called covalent compounds not held together because of opposite charges
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Molecular compounds name tells you the number of atoms Uses prefixes to tell you the number
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1 mono- 2 di- 3 tri- 4 tetra- 5 penta- 6 hexa- 7 hepta- 8 octa-
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9 nona- 10 deca-
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9 nona- 10 deca- To write the name write two words PrefixnamePrefixname-ide
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9 nona- 10 deca- To write the name write two words One exception is we don’t write mono- if there is only one of the first element. PrefixnamePrefixname-ide
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9 nona- 10 deca- To write the name write two words One exception is we don’t write mono- if there is only one of the first element. No double vowels when writing names (oa oo) except with i PrefixnamePrefixname-ide
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N 2 O NO 2 Cl 2 O 7 CBr 4 CO 2 BaCl 2
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diphosphorus pentoxide tetraiodide nonoxide sulfur hexaflouride nitrogen trioxide carbon tetrahydride phosphorus trifluoride aluminum chloride
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Writing names and Formulas
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Compounds that give off hydrogen ions when dissolved in water. Must have H in them will always be some H next to an anion HCl H 2 SO 4 The anion determines the name
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AnionExampleAcidExample ….ideCl - 1 chloride Hydro…icHCl Hydrochloric acid …..iteClO2 - 1 chlorite ….ousHClO 2 Chlorous acid Hypo…..iteClO -1 hypochlorite Hypo….ousHClO Hypochlorous acid …..ateClO 3 - 1 chlorate ….icHClO 3 Chloric acid Per…ateClO 4 - 1 perchlorate Per……icHClO 4 Perchloric acid
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Rule 1: If the anion attached to hydrogen is ends in -ide, put the prefix hydro- and change -ide to -ic acid Example: HCl - hydrogen ion and chloride ion Example: H 2 S hydrogen ion and sulfide ion
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If the anion has oxygen in it it ends in -ate of -ite Rule 2: change the suffix -ate to -ic acid Example: HNO 3 Hydrogen and nitrate ions Rule 3: change the suffix -ite to -ous acid Example: HNO 2 Hydrogen and nitrite ions
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HF H 3 P H 2 SO 4 H 2 SO 3 HCN H 2 CrO 4
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Hydrogen will always be first name will tell you the anion make the charges cancel out. Rule 1: hydro- no oxygen, -ide ion Rule 2 : no hydro, -ate comes from -ic, Rule 3: no hydro -ite comes from -ous
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hydroiodic acid acetic acid carbonic acid phosphorous acid hydrobromic acid
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A solid compound with a specific number of water molecules bonded to it Release water when heated at fairly low temperatures Anhydrous SolidxH2O) Common Example: CuSO 4 5H 2 O Copper (II) sulfate pentahydrate The penta indicates five water molecules for each copper (II) sulphate particle
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The prefix indicates the number of water molecules bonded to the anhydrous salt
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zinc sulphate heptahydrate copper (I) sulphite monohydrate cobalt (II) fluoride tetrahydrate lithium nitrate trihydrate sodium sulphate decahydrate calcium nitrate trihydrate
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Na2SO4 10H2O LiNO3 3H20 Cu2SO3 3H20 Ca(N03) 2 2H20 MgS04 7H20 ZnS04 7 H20
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