Naming Compounds Handout

Naming Compounds Handout IONIC COMPOUNDS versus MOLECULAR COMPOUNDS ionic compound: consist of cations (positive ions) and anions (negative ions) held together by electrostatic attraction – usually metal + nonmetal(s) – made of monatomic ions, polyatomic ions, and/or both – monatomic ions: consist of a single atom – polyatomic ions: consist of more than one atom molecular compound: consist of nonmetal atoms bonded together by shared electrons (covalent bonding) – acid: a molecular compound that releases + hydrogen ions (H ) when dissolved in water NAMING MONATOMIC CATIONS: Metal atoms lose valence electrons to form positively charged ions, called cations. An ion formed from an individual atom is a monatomic (or monoatomic) cation. I. Groups IA, IIA, IIIA elements silver (Ag), and zinc (Zn) form only one type of ion: + + + + – Group IA elements form +1 ions: H , Li , Na , K +2 +2 +2 +2 +2 – Group IIA elements form +2 ions: Be , Mg , Ca , Sr , Ba +3 – Group IIIA elements form +3 ions: Al + +2 – silver ion = Ag ; zinc ion = Zn When a Group IA, IIA, IIIA element, silver, or zinc forms an ion, it is named: element name + ion e.g. + Na = sodium ion +2 Sr = strontium ion +2 Zn = zinc ion page 1 of 12 II. The Stock system is used to name transition metals and other metals that form more than one ion: +2 +3 – iron (Fe) forms two ions: Fe and Fe +2 +4 – lead (Pb) forms two ions: Pb and Pb When a metal can form more than one ion, each ion is named: element name (charge in Roman numerals) + ion e.g. +2 Fe = iron (II) ion +3 Fe = iron (III) ion +2 Pb = lead (II) ion +4 Pb = lead (IV) ion + Cu = copper (I) ion +2 Cu = copper (II) ion Name each of the following monatomic cations: + Li = _________________________ Ag Al + +3 Mn +2 = ________________________ Mg = ________________________ = ________________________ + K = ________________________ Ca +2 = ________________________ Sn = _________________________ +2 Cu + +3 +2 = _________________________ H = _________________________ Fe Ba +2 +4 Co = _________________________ = _________________________ = _________________________ +3 = _________________________ + Na = _________________________ Ti +4 Ni +2 = _________________________ = _________________________ page 2 of 12 NAMING MONATOMIC ANIONS: Nonmetal atoms gain valence electrons to form negatively charged ions called anions. When a nonmetal forms an ion, it is named: element stem name + “ide” + ion e.g. O = oxygen atom N = nitrogen atom ⇒ ⇒ –2 O = oxide ion –3 N = nitride ion Name each of the following monatomic anions: – F = _________________________ – Br = _________________________ – I = _________________________ – Cl = _________________________ S P –2 –3 = _________________________ = _________________________ NAMING POLYATOMIC IONS: Ions made up of more than one atom are polyatomic ions: + – only one polyatomic cation: NH4 = ammonium ion – many polyatomic anions: see table below NH4+= ammonium ion – OH = hydroxide ion – CN = cyanide ion –2 CrO4 = chromate ion –2 Cr2O7 = dichromate ion Polyatomic Ions – NO2 = nitrite ion – NO3 = nitrate ion –2 SO4 –2 SO3 – C2H3O2 = acetate ion –3 PO4 = phosphate ion – = sulfate ion MnO4 = permanganate ion = sulfite ion CO3 –2 = carbonate ion – HCO3 = hydrogen carbonate ion or bicarbonate ion page 3 of 12 Name each of the following polyatomic ions: – CN = _________________________ SO4 –2 CrO4 –2 = _______________________ – = _________________________ NO3 = ________________________ – OH = _________________________ PO 4 + –3 = ________________________ – NH 4 = _________________________ C 2H3O 2 = _____________________ WRITING CHEMICAL FORMULAS GIVEN INDIVIDUAL IONS Compounds must be neutral ⇒ total +ve charge = total –ve charge 1. If the two ions have exactly opposite charges (+1 and –1, +2 and –2, +3 and –3) ⇒ formula of the compound contains one of each ion + e.g. – Na Ca + Cl +2 +3 Al –2 + S –3 + N ⇒ ⇒ ⇒ + NaCl – K CaS Ba +2 Fe KNO3 –2 ⇒ BaSO4 –3 ⇒ FePO4 + SO4 +3 AlN ⇒ + NO3 + PO4 Combine each pair of ions to get the formula of the compound they form: NH4 Sr +2 Na Ni + + +2 Cu +2 + F – ⇒ + CO3 –2 + C2 H 3 O 2 ⇒ – ⇒ _____________ _____________ Li + Al K + CN +3 + ⇒ _____________ Fe –2 ⇒ _____________ Co – + PO4 + OH –2 + CrO4 + SO4 _____________ +3 +3 + N ⇒ –3 – ⇒ _____________ _____________ ⇒ _____________ –3 ⇒ _____________ –3 ⇒ _____________ + P page 4 of 12 2a. If two monatomic ions have different charges ⇒ use crossover rule to get formula of the compound – superscript for cation becomes subscript for anion – superscript for anion becomes subscript for cation – simplify subscripts to get lowest ratio of atoms (Note: Only the numbers cross down, not the signs!) > Ba2+ N3– Ba3N2 2– 4+ Ti O> TiO2 > > Na+ S 2– Na2S > Ti2O4 is simplified! b. If two ions have different charges and at least polyatomic ion is involved use crossover rule to get formula of the compound – if more than one of polyatomic ion in formula, use parentheses – simplify subscripts to get lowest ratio of atoms (Note: Again only the numbers cross down, not the signs!) ⇒ 2– NH+4 O (NH4)2O 2+ – Ca NO3> Ca(NO3)2 4+ 2– Pb> CO3> Pb(CO3)2 > Pb2(CO3)4 is simplified! Combine each pair of ions to get the formula of the compound they form: Cu Li + + –2 O CO3 –2 Sn +4 +3 Fe SO4 –2 –2 S + K +2 Ni –3 P PO4 –3 page 5 of 12 CHEMICAL FORMULAS AND NAMES FROM INDIVIDUAL IONS Compounds are named from the individual ions they come from. Name the cation and the anion, then remove “ion” from each name: + e.g. Na = sodium ion – Cl = chloride ion ⇒ NaCl = sodium chloride + K = potassium ion –2 CO3 = carbonate ion ⇒ K2CO3 = potassium carbonate +3 Fe = iron (III) ion – NO3 = nitrate ion ⇒ Fe(NO3)3 = iron (III) nitrate + Ag = silver ion –2 S = sulfide ion ⇒ Ag2S = silver sulfide Combine each pair of ions to get the chemical formula, then name the compound: Individual ions Mg Ni +2 Ca Al +2 +3 Co K +2 +2 + Fe – F –2 S Br – –3 P NO2 CrO4 +3 O – –2 –2 Compound Formula Compound Name _____MgF2______ ______magnesium fluoride_____ _______________ ___________________________ _______________ ___________________________ _______________ ___________________________ _______________ ___________________________ _______________ ___________________________ _______________ ___________________________ page 6 of 12 GIVEN THE CHEMICAL FORMULA, NAME THE COMPOUND 1. If the metal is in Groups IA–IIIA, silver, cadmium, or zinc, then just name the metal cation and the anion: e.g. NaCl ⇒ Na = sodium and Cl = chloride ⇒ sodium chloride BaI2 ⇒ Ba = barium and I = iodide ⇒ barium iodide Al(OH)3 ⇒ Al = aluminum and OH = hydroxide ⇒ aluminum hydroxide ZnSO4 ⇒ Zn = zinc and SO4 = sulfate ⇒ zinc sulfate 2. If the metal can form more than one ion, a. Determine the charge on the cation using the charge on the anion. b. Name the cation and the anion, then remove “ion” from both e.g. Ni Br2 ⇒ Ni +2 ⇒ ⇒ Since the ion formed is Br–, then 2 Br’s have an overall negative charge of –2. To get an overall charge of zero for the compound, the overall positive charge must be +2. Thus, Ni must have a +2 charge of +2, so the ion nickel forms is Ni . – = nickel (II) ion Br = bromide ion NiBr2 = nickel (II) bromide c. If a polyatomic ion is involved, remember that more than one polyatomic is shown in parentheses—i.e. DO NOT multiply the charge of the polyatomic ion with the subscript of the atoms in a polyatomic ion. CuSO4 ⇒ There is only ONE Cu and ONE SO4, so get the charge –2 for the Cu based on the SO4. The formula is SO4 , and –2 there is only ONE SO4 , so Cu’s charge here must be +2 for the compound to have an overall charge of zero. +2 –2 ⇒ Cu = copper (II) ion SO4 = sulfate ion then ⇒ CuSO4 = copper (II) sulfate page 7 of 12 Give the name for each compound given its chemical formula: Formula MgCl2 Individual Ions +2 Mg Name of Compound Cl– magnesium chloride LiOH ZnCO3 K2S FePO4 SnO2 CuBr2 Ag3N Mn(CN)2 AgC2H3O2 WRITING CHEMICAL FORMULAS GIVEN THE COMPOUND NAME Get the individual ions from the name, then combine them using the crossover rule: e.g. barium chloride ⇒ Ba+2 Cl– aluminum sulfate ⇒ +2 – barium = Ba chloride = Cl BaCl2 ⇒ +3 aluminum = Al Al+3 SO4–2 ⇒ sulfate = SO4 –2 Al2(SO4)3 page 8 of 12 Give the chemical formula for each compound given its name: Name of Compound individual ions lithium cyanide Li + CN – Formula LiCN iron (III) sulfate calcium iodide tin (IV) dichromate silver nitrite copper (II) acetate zinc carbonate lead (II) phosphide potassium sulfite cobalt (II) nitride nickel (II) permanganate NAMING MOLECULAR COMPOUNDS Indicate number of atoms of each element with Greek prefix before element name: # of atoms Greek Prefix # of atoms Greek Prefix 1 mono (usually omitted) 6 hexa 2 di 7 hepta 3 tri 8 octa 4 tetra 9 nona 5 penta 10 deca page 9 of 12 For the first element: For the second element: Note: Greek prefix + element name Greek prefix + element name stem + “-ide” Mono is generally omitted, except in common names like CO = carbon monoxide P2O5 SF6 diphosphorus pentaoxide sulfur hexafluoride Name the following molecular compounds: SO3 = _____________________ SiBr4 = ______________________ XeF6 = ______________________ ClF3 = ______________________ N2O4 = ______________________ Cl2O7= ______________________ PCl5 = ______________________ P4O10 = _____________________ DETERMINING FORMULAS OF MOLECULAR COMPOUNDS Use Greek prefix(es) to determine number of atoms of each element in formula. Get elements and number of atoms of each from name: tetraphosphorus hexasulfide P 4 S6 page 10 of 12 Give the formulas for each of the following molecular compounds: nitrogen trichloride dibromine heptaoxide dinitrogen pentasulfide DETERMINING FORMULAS AND NAMES OF ACIDS FROM IONS Given an ion, we can get formula of acid by: we can name for acid: – F = fluoride ion – NO2 = nitrite ion SO4 –2 adding H atoms equal to negative charge on ion depending on suffix of ion name add # of H's equal to negative charge HF (aq) = hydrofluoric acid add # of H's equal to negative charge HNO2 (aq) = nitrous acid add # of H's equal to negative charge = sulfate ion H2SO4 (aq) = sulfuric acid Name each of the following ions, and determine the formula and name of the corresponding acid that forms from the ion. Name of Ion CO3 –2 = __carbonate ion___ Formula of Acid ⇒ __ H2CO3__ (aq) = ____ carbonic acid______ – Cl = _________________ ⇒ ____ SO3 PO4 –2 –3 Name of Acid ____ (aq) = _______________________ = _________________ ⇒ _________ (aq) = _______________________ = _________________ ⇒ _________ (aq) = _______________________ – NO3 = __________________ ⇒ __________ (aq) = ______________________ page 11 of 12 Name each of the following acids: HBr (aq)= _________________ H2CrO4 (aq)= ___________________ H2S (aq)= _________________ HC2H3O2 (aq)= _________________ HF (aq)= _________________ H2SO4 (aq)= ___________________ Give the formula for each of the following acids: [Don’t forget to indicate (aq)!] phosphoric acid = ___________ nitrous acid = ___________ hydroiodic acid = ___________ carbonic acid = ___________ sulfurous acid = ___________ nitric acid = ___________ PUTTING IT ALL TOGETHER: Name each of the following compounds: BaCl2 _____________________ NiBr2 ____________________ HNO3(aq)_____________________ SO2 ____________________ AgF PbS2 ____________________ CuSO3 _____________________ PF5 ____________________ K2SO4 _____________________ Cr(C2H3O2)3________________ FeP _____________________ Al2(CO3)3 ___________________ NiSO4 _____________________ Zn(OH)2 __________________ KMnO4 _____________________ Sn(CN)2 __________________ _____________________ page 12 of 12