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CHEMISTRY Naming Compounds Handout page 1 ANSWER KEY 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) o - rather large difference in electronegativity of the bonding elements – made of monatomic ions, polyatomic ions, and/or both – monatomic ions: consist of a single atom {e.g. Na+ or F-} - polyatomic ions: consist of more than one atom {e.g. OH-, NH4+ } Molecular compound: consist of nonmetal atoms bonded together by shared pairs electrons (covalent bonding) – acid: a molecular compound that releases hydrogen ions (H+) when dissolved in water {often appears as hydronium ion; H3O+(aq)} NAMING MONATOMIC CATIONS: Metal atoms tend to lose valence electrons to form positively charged ions, called cations. An positive ion formed from an individual atom is a monatomic cation. - Groups IA, IIA, IIIA (B+3, Al+3, Ga+3) zinc (Zn+2), cadmium (Cd+2), and silver (Ag+), form only one type of ion (have one oxidation number): – Group IA elements form +1 ions: H+, Li+, Na+, K+, Rb+, Cs+ – Group IIA elements form +2 ions: Be+2, Mg+2, Ca+2, Sr+2, Ba2+ - Group IIIA elements forming +3 ions: B+3, Al+3, Ga+3 - Transition elements forming only one positive ion: Ag+, Zn2+, Cd+2 CHEMISTRY Naming Compounds Handout page 2 When a Group IA, IIA, IIIA (first three elements), cadmium, zinc, or silver forms an ion, it is named: element name + ion/cation e.g. Na+ = sodium ion Sr+2 = strontium cation Zn+2 = zinc ion The Stock system or traditional system is used to name transition metals, post transition metals, and other metals that form more than one positive ion (have multiple oxidation numbers): e.g. Iron forms Fe+2 and Fe+3 Lead forms Pb2+ and Pb4+ When a metal can form more than one ion, each ion is named in the Stock System by: Element name (charge in Roman numerals) & ion/cation Fe+2 is the iron (II) ion and Fe+3 is the iron (III) cation Pb2+ is lead (II) ion and Pb4+ is the lead (IV) cation Some of the metallic ions are named in the Traditional System using the root of their name of origin or anglicized name with an –ous or –ic suffix attached. The –ous suffix is used with the ion of lesser positive charge and the –ic suffix is used with the ion of greater positive charge. The name of origin for iron is ferrum and that of lead is plumbum. Fe+2 is the ferrous cation and Fe+3 is the ferric ion Pb2+ is the plumbous cation and Pb4+ is the plumbic ion Other elements of which to be aware are: copper – cuprum, tin – stannum, and mercury which is hydragyrum BUT IT FORMS a MERCUROUS and a MERCURIC ION CHEMISTRY Naming Compounds Handout page 3 **Look up the above elements to determine the cations that they form! Also, look up the cobaltous/cobaltic ions and the chromous/chromic ions Name each of the following monatomic cations: Li+ - lithium ion Ag+ - silver ion Ba+2 – barium cation Cu+2 (both names) – copper(II) ion/cupric cation Al3+ - aluminum cation Mg++ - magnesium ion Mn+2 - manganese(II) cation Mn+7 – manganese(VII) ion Mn+5 - manganese(V) ion Mn+4 - manganese(IV) cation Sn4+ (both names) – tin(IV) ion/stannic cation Sn+2 (both names)- tin(II) ion/ Stannous cation Co++- cobalt(II) ion/cobaltous ion Co+++- cobalt(III) ion/cobaltic cation Na+1- sodium cation K1+ - potassium cation Ni+2 - nickel ion Ca+2 – calcium ion Ti+4 - titanium(IV) cation Cd+2 - cadmium cation NAMING MONATOMIC ANIONS: Nonmetal atoms tend to gain valence electrons to form negatively charged ions called anions. When a nonmetal forms an ion, it is named: Element root name - “ide” & ion/anion e.g. O = oxygen atom which forms the O–2 = oxide ion/anion N = nitrogen atom which forms the N–3 = nitride ion/anion CHEMISTRY Naming Compounds Handout page 4 Name each of the following monatomic anions: F- - fluoride ion Cl- - chloride ion S2- - sulfide anion P-3 – phosphide anion I- - Iodide anion Te - - - telluride ion As3- - arsenide anion Se-2 – selenide ion Br- - bromide anion C4 - - carbide ion NAMING POLYATOMIC IONS: Ions made up of more than one atom (covalently bonded) are polyatomic ions. These ions function as a single unit: – only one polyatomic cation: NH4+ = ammonium ion - Also be aware of the mercurous ion which is a diatomic ion; Hg22+ – there are many polyatomic anions: see table below: Polyatomic cations NH4+ is the ammonium ion Polyatomic anions – most of these are oxyanions (negatively charged and contain oxygen bonded to a central atom) – many of these ions end in –ate or -ite NO2- = nitrite ion NO3- = nitrate ion MnO41 - = permanganate ion ClO3-1 = chlorate HCO3-1 = hydrogen carbonate or bicarbonate ion ClO4- = perchlorate ClO2-1 = chlorite ClO- = hypochlorite HSO4- = hydrogen sulfate or bisulfate C2H3O2- = acetate ion BrO3- = bromate IO3- = iodate SCN- = thiocyanate HSO3- = bisulfite or hydrogen sulfite CHEMISTRY Naming Compounds Handout page 5 Some are nonoxyanions; these end in “–ide” OH– = hydroxide ion CN- = cyanide ion N3- = azide NH2- = amide O2-2 = peroxide ion Negative two CrO4-2 = chromate ion SO4-2 = sulfate ion CO3-2 = carbonate ion Cr2O7-2 = dichromate ion SO3-2 = sulfite ion SeO4-2 = selenate ion TeO4-2 = tellurate ion SiO3-2 = silicate ion C2O4-2 = oxalate ion S2O3-2 = thiosulfate ion Negative three PO4- 3 = phosphate ion AsO4 -3 = arsenate ion BO3-3 = borate Some of the oxyanions follow a system of naming: Oxyanion – a negatively charged oxygen bearing ion The most common ion is often from the “– ate” group of ions – memorize these ions!! If the ion’s central atom increases in charge or an oxygen is added compared to the _ate form, retain the charge and the name of the ion will be: per-__________-ate If the ion’s central atom decreases in charge or an oxygen is lost from the – ate form of the ion, the name of the ion becomes: _________ - ite If the ion’s central atom decreases in charge or an oxygen is lost from the – ite form the ion becomes: hypo - __________ - ite CHEMISTRY Naming Compounds Handout page 6 Example Name Formula Charge on central atom perchlorate ClO4 - Cl chlorate ClO3 - Cl +5 chlorite ClO 2 - Cl +3 hypochlorite ClO - Cl +7 +1 Name each of the following polyatomic ions: ClO- = hypochlorite ion Cr2O7-2 = dichromate ion OH- = hydroxide ion CO3-2 = carbonate ion PO4-3 = phosphate ion BO3-3 = borate ion SeO4-2 = selenate ion NO3- = nitrate ion HSO3- = bisulfite/hydrogen sulfite ion CN- = cyanide ion CrO4-2 = chromate ion O2-2 = peroxide ion WRITING CHEMICAL FORMULAS GIVEN INDIVIDUAL IONS **All compounds must be electrically neutral (electroneutrality). Therefore, the total positive charge in the compound {# positive ions x the charge on each ion} must equal the total negative charge (# of negative ions x the charge on each ion} in the compound.** Subscripts are manipulated to obtain the simplest ratio of ions that will produce a neutral chemical formula! CHEMISTRY Naming Compounds Handout page 7 1. If the two ions have exactly the same, but opposite charges (+1 and –1, +2 and –2, +3 and –3) then by “simple inspection” there must be one of each ion present in the formula. Combines in a 1 to 1 ratio. e.g. Na+ & I- combine to form NaI Mg+2 & O-2 combine to form MgO Al+3 & N-3 combine to form AlN 2. If two monatomic ions have different charges; Identify the charge on each of the combining ions. a. Use trial and error e.g. Ca+2 & F- Start with 1 to 1 ratio CaF one (+2) and 1 (- 1) = + 1 net charge therefore, not correct – excessive positive charge so increase the number of negative ions CaF2 one (+ 2) and 2 (- 1) = 0 for net charge therefore, correct formula! b. Use the least common multiple of the absolute values of the charges on the ions e.g. combining potassium (K+) and phosphate (PO4-3) The LCM of │+1│ and │-3│ is 3 To obtain the subscripts of the ions, divide the LCM by the absolute value of the charge on that ion and use the result as a subscript For potassium’s subscript: 3 / │1 │= 3 For phosphate’s subscript: 3 / │- 3│ = 1 The formula will be K3PO4 CHEMISTRY Naming Compounds Handout page 8 c.Use crossover rule (criss-cross) to get formula of the compound – the absolute value of the superscript for cation becomes subscript for anion - the absolute value of the superscript for anion becomes subscript for cation (Note: Only the numbers cross down, not the signs!) Beware - simplify subscripts to get simplest ratio of ions, excepting mercury(I) Ionic compounds are usually represented by empirical formulas e.g combining nickel(II) and iodine Ni+2 and IUse the 2 for the subscript of iodine and the 1 for the subscript of nickel to get NiI2 Ni+2 I-1 Recall, a subscript of one (1) is NEVER EXPRESSED – it is redundant!! e.g combining magnesium (Mg+2) and carbonate (CO3-2) Use the two for the subscript of magnesium and the two for the subscript of carbonate to produce Mg2(CO3)2. HOWEVER, these subscripts need to be reduced to form MgCO3. Recall: if only one polyatomic ion is present in the formula, no parentheses are used. But, if two or more polyatomic ions are present, the formula of the ion is placed inside parentheses and the subscript is placed outside!! CHEMISTRY Naming Compounds Handout page 9 Naming Compounds In order to correctly name a compound, the appropriate nomenclature system must be utilized. Therefore, the first step is identifying the compound; is it organic, ionic, molecular, an acid, or a hydrate. Ionic compounds – metal – nonmetal; metal – polyatomic anion; or polyatomic cation – polyatomic anion; polyatomic cation - nonmetal Molecular compounds – nonmetal – nonmetal; hydrogen - polyatomic ion; hydrogen – nonmetal Acids – solubilized hydrogen – nonmetal; solubilized hydrogen – polyatomic ion Solubilized – meaning dissolved in water, and therefore, usually represented with an (aq) phase symbol Hydrates – ionic salts with water molecules weakly attached Organic – carbon based in which C is covalently bonded, mainly with hydrogen (H). However, organic compounds may at times contain some nitrogen (N), sulfur (S), phosphorus (P), oxygen (O). NOTE EXCEPTIONS are CO, CO2, and CO32Ionic compounds – Name the positive ion (cation) first If a polyatomic ion, merely write its name If a metal from Groups I A or II A, IIIA (B, Al, Ga), or Zn, Cd, Ag; merely write the metal’s name Any other metal, determine the charge on the metallic ion and use either its traditional name (-ic/ous) or the Stock name (Roman numeral in parentheses) To determine the charge on the metal ion: 1) Determine total negative charge in the formula (compound). 2) Change the negative sign to a positive sign as all compounds are neutral, therefore total negative charge MUST EQUAL total positive charge 3) Divide the total positive charge by the number of metallic ions to get the charge per cation Note – in all cases, the term ion is omitted!! CHEMISTRY Naming Compounds Handout page 10 Name the negative ion last If a nonmetal, modify its name for the –ide suffix If a polyatomic ion, merely write its name e.g. MgCl2 – magnesium chloride e.g. FeSO3 – iron (II) sulfite or ferrous sulfite e.g. (NH4)2CO3 – ammonium carbonate Molecular compounds – Binary compounds composed of two nonmetals. Traditional naming uses prefixes to indicate the number of atoms of each element present in a molecule of the compound Mono-; di-; tri-; tetra-; penta-; hexa-; hepta-; octa-; nona-; decaNOTES - The mono- is dropped on the more positive element and the vowel of a two syllable prefix is dropped if the nonmetal name begins with a vowel Stock naming is similar to that used for ionic compounds The more positive element is named first followed by the more negative element modified for the –ide suffix e.g. N2O5 – dinitrogen pentoxide or nitrogen (V) oxide e.g. PCl3 – phosphorus trichloride or phosphorus (III) chloride NOTE: use the traditional or use the Stock, but do not combine the two! Organic Organic compounds have their own unique nomenclature system based upon the type of organic compound. Alkanes – CnH2n+2 ; Alkenes - CnH2n ; Alkynes - CnH2n-2 ; alcohols which contain an OH (hydroxyl group) CHEMISTRY Naming Compounds Handout page 11 Prefixes based upon the number of carbon atoms in a chain: meth-, eth,prop-, but-, pent-, hex-, hept-, oct-, non-, decAlkanes attach a, “-ane” suffix or ending to the prefix Alkenes attach an “-ene” suffix or ending to the prefix Alkynes attach an “-yne” suffix or ending to the prefix Alcohols attach an “-anol” to the prefix In addition, numbers are used to indicate position of the double bond, triple bond, or –OH group in an alcohol. e.g. 2-pentene Acids – the are often solubilized (dissolved in water) molecular compounds e.g. HCl(aq), HNO3(aq), H2SO4(aq) Naming acids Binary acids are composed of hydrogen and a nonmetallic element They are named using the form: hydro – nonmetal root – ic This form is also used by any non-oxyacid as well e.g. HCl(aq) – hydrochloric acid H2S(aq) – hydrosulfuric acid HI(aq) – hydroiodic acid Oxyacids contain hydrogen and an oxyanion (negative polyatomic ion w/ oxygen bonded to a central atom (often a nonmetal)) They are named using the form: anion prefix – anion root – ic/-ous (if present) CHEMISTRY Naming Compounds Handout page 12 The –ate ions become –ic acids and the –ite ions become –ous acids e.g. HNO3 – nitric acid HNO2 – nitrous acid H2SO4 – sulfuric acid H2SO3 – sulfurous acid HClO4 – perchloric acid HClO – hypochlorous acid Hydrates – these are ionic salts that have water molecules weakly attached to them in a specific ratio These “waters of hydration” are usually driven off by heating the hydrate which leaves the anhydrous residue (ionic salt) Note the form of a hydrated compound’s formula Anhydrous salt formula • coefficient water’s formula e.g. MgSO4 • 7 H2O CuSO4 • 5 H2O Naming these hydrates involves writing the name of the anhydrous salt first followed by a prefix attached to the word hydrate. The Greek prefix refers to the coefficient before the formula of water. The word hydrate refers to water. The names of the compounds above would respectively be: magnesium sulfate heptahydrate copper (II) sulfate pentahydrate or cupric sulfate pentahydrate What would be the anhydrous salt that remains after heating the above hydrates? magnesium sulfate and copper(II) sulfate or cupric sulfate How is a hydrate different from other chemical compounds? Hydrates contain water molecules present in the structure in a defined ratio per formula unit of salt Define the following terms: Anhydrous – without water/containing no water CHEMISTRY Naming Compounds Handout page 13 Dehydration – to remove water Name the following compounds: a) FeCl3 • 6 H2O _ferric chloride hexahydrate/iron(III) chloride hexahydrate b) BaCl2 • 2 H2O barium chloride dihydrate Write the formulas for the following compounds: a) sodium carbonate decahydrate _Na2CO3 • 10 H2O__ b) strontium chloride hexahydrate _SrCl2 • 6 H2O___ Name the following compounds 1) Na2CO3 _sodium carbonate________ 2) NaOH _sodium hydroxide__________ 3) HBr _hydrogen bromide _______ 4) MgBr2 _magnesium bromide__________ 5) KCl _potassium chloride_____________ 6) N2S3 _dinitrogen trisulfide/nitrogen(III) sulfide_______ 7) FeCl2 _iron(II) chloride/ferrous chloride_________ 8) FeCl3 _iron(III) chloride/ferric chloride______ 9) SiF4 _silicon tetrafluoride/silicon(IV) fluoride_____ 10) Zn(OH)2 _zinc hydroxide___________________________ 11) BeSO4 _beryllium sulfate____________________________ 12) SO3 _sulfur trioxide/sulfur(VI) oxide___________ 13) HClO3(aq) _chloric acid____________ 14) N2O3 _dinitrogen trioxide/nitrogen(III) oxide_____________ CHEMISTRY Naming Compounds Handout 15) Al2S3 _aluminum sulfide_____________________________ 16) PbO _plumbous oxide/lead(II) oxide_________ 17) HBr(aq) _hydrobromic acid_______ 18) Li3PO4 _lithium phosphate________ 19) TiI4 _titanium(IV) iodide________ 20) Co3N2 _cobalt(II) nitride/cobaltous nitride__________ 21) Mg3P2 __magnesium phosphide______________ 22) Ga(NO2)3 _gallium nitrite________________ 23) Ag2SO3 _silver sulfite____________ 24) H2S(aq) _hydrosulfuric acid____________ 25) NH4OH ammonium hydroxide________ 26) Al(CN)3 _aluminum nitrate_____________ 27) Be(CH3COO)2 _beryllium acetate_________ 28) NO _nitrogen monoxide/nitrogen(II) oxide________ 29) P4O10 _tetraphosphorus decoxide__________ 30) H2SO4(aq) _sulfuric acid____________ page 14 Write chemical formulas for the following compounds 1) copper (II) chloride _CuCl2________________________ 2) lithium acetate _LiC2H3O2____________________________ 3) nitrous acid _HNO2(aq) _______________________________ 4) vanadium (III) selenide _V2Se3______________________ 5) sulfur hexachloride _SCl6_________________________ 6) manganese (IV) nitride _Mn3N7______________________ 7) beryllium oxide _BeO____________________________ CHEMISTRY Naming Compounds Handout 8) chlorous acid __HClO2(aq)_____________________________ 9) sulfur dioxide _SO2______________________________ 10) sodium sulfate _Na2SO4_____________________________ 11) aluminum arsenide _AlAs__________________________ 12) diboron hexahydride _B2H6________________________ 13) potassium permanganate _KMnO4______________________ 14) chromium (VI) cyanide __Cr(CN)6______________________ 15) hydrobromic acid __HBr(aq)____________ 16) tin (II) sulfite _SnSO3_______________ 17) vanadium (V) fluoride _VF5____________ 18) nitrogen tribromide _NBr3_____________ 19) ammonium nitrate _NH4NO3____________ 20) diphosphorus pentoxide _P2O5___________ Write the names of the following compounds 1) NaBr _sodium bromide__________ 2) Ca(C2H3O2)2 _calcium acetate__________ 3) P2O5 _diphosphorus pentoxide_________ 4) Ti(SO4)2 __titanium(IV) sulfate___________ 5) FePO4 __iron(III) phosphate/ferric phosphate_____ 6) K3N _potassium nitride________ 7) SO2 _sulfur dioxide/sulfur(IV) oxide_________ 8) CuOH _copper(I) hydroxide/cuprous hydroxide____ 9) Zn(NO2)2 _zinc nitrite_________________ page 15 CHEMISTRY Naming Compounds Handout page 16 10) V2S3 _vanadium(III) sulfide_________________ 11) CoCl2 • 2 H2O _cobalt(II) chloride dehydrate or cobaltous chloride dihydrate_ 12) NiSO3 • 6 H2O _nickel(II) sulfite hexahydrate _____ Write chemical formulas for the following compounds. 13) silicon dioxide _SiO2_______________________ 14) nickel (III) sulfide _Ni2S3___________________ 15) manganese (II) phosphate _Mn3(PO4)2______ 16) silver acetate _AgC2H3O2___________ 17) diboron tetrabromide _B2Br4_________ 18) cupric chloride dihydrate _CuCl2 • 2 H2O______ 19) potassium carbonate _K2CO3__________ 20) ammonium chlorate _NH4ClO3__________ 21) tin (IV) selenide _SnSe2______________ 22) carbon tetrachloride _CCl4___________________ 23) barium iodide dihydrate _BaI2 • 2 H2O_______