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IONIC COMPOUNDS: Names and Formulas

IONIC COMPOUNDS: Names and Formulas. Naming compounds in chemistry is called NOMENCLATURE. There are a few general rules that apply when naming ionic compounds. 1. Most ionic compounds are also called salts. 2. Most ionic compounds exist as solids and many dissolve to form aqueous solutions.

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IONIC COMPOUNDS: Names and Formulas

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  1. IONIC COMPOUNDS: Names and Formulas

  2. Naming compounds in chemistry is called NOMENCLATURE

  3. There are a few general rules that apply when naming ionic compounds. 1. Most ionic compounds are also called salts. 2. Most ionic compounds exist as solids and many dissolve to form aqueous solutions. 3. An ionic compound is made up of a metal and a nonmetal; metals are located on the left side of the periodic table and nonmetals are on the right side. 4. The cation (positive ion) is written first followed by the anion (negative ion). 5. Before naming compounds, you should first memorize the individual cations and anions.

  4. Nomenclature of ionic compounds • There are two types of ionic compounds depending on the cations. • Type 1 or “fixed oxidation state” cations – only form one cation • Groups IA to IIIA and the elements silver (Ag), zinc (Zn) and cadmium (Cd) form only one type of ion each: • – Group IA elements form +1 ions: Li+, Na +, K +, Rb +, Cs + • – Group IIA elements form +2 ions: Be +2, Mg +2, Ca +2, Sr +2, Ba +2 • – Group IIIA elements form +3 ions: Al +3 • – silver ion = Ag +; zinc ion = Zn +2; cadmium ion = Cd +2 • Type 2 or “variable oxidation state” cations - can form multiple cations

  5. Monatomic Charges The charge of the individual ions in a salt should add up to zero, the overall charge of the compound. For example NaCl is composed of Na+ ions and Cl- ions. For every one sodium ion you need one chloride ion (+1) + (-1) = 0 Ba2+ and N3- : You need 3 (+2 ) Barium ions to cancel out the 2 (-3) nitride ions so the overall charge of the compound is zero. Nomenclature of binary ionic compounds Name the metal then the root of the nonmetal + ide ending:

  6. Binary ionic compound ROOTS

  7. Nomenclature of binary ionic compounds NaCl Sodium chloride BaCl2 Barium chloride H2S Hydrogen sulfide Mg3N2 Magnesium nitride NaF Sodium fluoride K2O Potassium oxide • Notice that the cation is always mentioned first and then the anion. • Notice that the anion always ends in -ide • Notice that the number of elements in the compound is not mentioned in the name. Name the following ionic compounds: Na2O K2S MgBr2 AlN Ba3As2 CaCl2 AgCl AlH3 ZnI2 Li3P

  8. Nomenclature of binary ionic compounds Answers: Na2O = sodium oxide K2S = potassium sulfide MgBr2 = magnesium bromide AlN = aluminum nitride Ba3As2 = barium arsenide CaCl2 = calcium chloride AgCl = silver chloride AlH3 = aluminum hydride ZnI2 = zinc iodide Li3P = lithium phosphide

  9. Polyatomic Ions Ions made up of more than one atom are polyatomic ions: The individual ions should add up to the overall charge of the polyatomic ion. What is the charge of Mn in MnO4-? 1 Mn + 4 O = -1 so 1(Mn) + 4 (-2) = -1 so Mn - 8 = -1 so Mn = +7 – only one polyatomic cation: NH4 + which is the ammonium ion – many polyatomic anions: ……next page (I will give you a list to memorize) • Note: the polyatomic ions must be memorized.

  10. Nomenclature of binary ionic compounds Some polyatomic anions that you must know: NO3- = nitrate NO2- = nitrite SO4 2- = sulfate SO32- = sulfite PO43- = phosphate PO33- = phosphite CO32- = carbonate HCO31- = hydrogen carbonate or bicarbonate OH- = hydroxide CN- = cyanide C2H3O2- = acetate C2O42- = oxalate

  11. Nomenclature of binary ionic compounds Naming salts composed of the polyatomic ions is the same as with the monatomic anions. Metal name then polyatomic name. NaOH sodium hydroxide Ba(NO3)2 barium nitrate H2SO4 hydrogen sulfate CsNO2 cesium nitrite Sometimes there is a common name: KHCO3potassium hydrogen carbonate or potassium bicarbonate Name the following ionic compounds: NaHCO3 K2SO3 MgSO4 KCN H2PO4 Ca(OH)2 NH4NO3 Zn(NO3)2 Li3PO4 HNO3

  12. Nomenclature of binary ionic compounds Answers: NaHCO3 = sodium hydrogen carbonate or sodium bicarbonate K2SO3 = potassium sulfite MgSO4 = magnesium sulfate KCN = potassium cyanide H2PO4 = hydrogen phosphate Ca(OH)2 = calcium hydroxide NH4NO3 = ammonium nitrate Zn(NO3)2 = zinc nitrate Li3PO4 = lithium phosphate HNO3 = hydrogen nitrate

  13. Early Names of Elements

  14. Nomenclature of binary ionic compounds The previous examples only named type 1 or “fixed oxidation state” cations. When naming type 2 or “variable oxidation state” cations the rules change. CuOHcopper(I) hydroxideFe(NO3)3iron(III) nitrate CuSO4copper(II) sulfate Sn(NO2)4tin(IV) nitrite Sometimes a common name exists: CuOHcuprous hydroxideFe(NO3)3ferric nitrate • When naming type 2 cations, the systematic method (IUPAC) requires the use of roman numerals after the elemental name to represent the oxidation state of the cation. The common name uses the –ic ending for the higher oxidation state and –ous ending for the lower oxidation state. Many times the old latin or greek name is used as the root. Name the following ionic compounds: CuHCO3 FeSO3 CuSO4 Cr(CN)3 Cr(PO4)2 Sn(OH)2 W(NO2)5 Ti(CO3)2 CoPO4 PbCl2

  15. Nomenclature of binary ionic compounds Answers: CuHCO3 = copper(I) hydrogen carbonate or cuprous bicarbonate FeSO3 = iron(II) sulfite or ferrous sulfite CuSO4 = copper(II) sulfate or cupric sulfate Cr(CN)3 = chromium(III) cyanide Cr(PO4)2 = chromium (VI) phosphate Sn(OH)2 = tin(II) hydroxide or stannous hydroxide W(NO2)5 = tungsten(V) nitrite Ti(CO3)2 = titanium(IV) carbonate CoPO4 = cobalt(III) phosphate or cobaltic phosphate PbCl2 = lead(II) chloride or plumbous chloride

  16. PRACTICE PROBLEMS Below the formula, give the systematic name for the following compounds. If a common name exist, write it below the systematic name. 1. KBr 2. BaO 3. Na2O 4.CaF3 5. Cr2S3 6. Ti(NO3)4 potassium bromide Sodium oxide Barium oxide calcium fluoride Titanium (IV) nitrate or titanic nitrate Chromium (III) sulfide The problem set continues on the next page.

  17. PRACTICE PROBLEMS Below the name, write the formula for the following compounds. Lithium chloride b) Aluminum sulfide e) Copper(II) oxide f) Iron(III) chloride i) Calcium bicarbonate l Potassium nitrite Potassium sulfate Ammonium carbonates s )Iron(II) phosphate w) Li + Cl - LiCl Al3+ S2- Al2S3 CuO Ca(HCO3)2 FeCl3 KNO2 K2SO4 (NH4)2CO3 Fe3(PO4)2

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