Modern Chemistry Chapter 7

Ch 7 Chemical Formulas & Chemical Compounds A website ( encourages people to sign a petition against a dangerous chemical called dihydrogen monoxide. Their reasoning…. DHMO is found in all cancer cells DHMO can cause serious burns DHMO is a major component of acid rain DHMO contributes to global warming Traces of DHMO have been found in every stream, river, lake, bay, and ocean Would you sign this petition? Why or why not?

Ch 7 Chemical Formulas & Chemical Compounds What is limestone? ammonia? sucrose? Do these common names provide any information about chemical composition? Chemists use systematic rules to name compounds and write chemical formulas to avoid confusion Note the similarity in purpose to Linnaeus’ system of binomial nomenclature to name organisms!

Ch 7 Chemical Formulas & Chemical Compounds Chemistry has a language all of its own EnglishChemistry Element SymbolsLetters Chemical FormulasWords Chemical EquationsSentences

7.1 Chemical Names & Formulas Objectives Explain the significance of a chemical formula Determine the formula of an ionic compound formed between two given ions Name an ionic compound given its formula Using prefixes, name a binary molecular compound from its formula Write the formula of a binary molecular compound given its name

7.1 Chemical Names & Formulas Chemical Formulas indicate the relative number of atoms of each kind in a chemical compound Molecular Formulas reveal the number of atoms of each kind in a molecular compound C4H10 4 carbon atoms, 10 hydrogen atoms in one molecule of butane Ionic Formulas Represent a formula unit, the simplest whole # ratio of cations to anions in a crystal lattice CaCl2 ratio of 1 Ca 2+ ion to two Cl -1 ions in the crystal lattice

7.1 Chemical Names & Formulas Let’s practice identifying the # and types of atoms in a compound….. NO2 C12H22O11 H2SO 4 Fe2O 3 (NH 4 )2CO 3 Al2(SO 4 ) 3

7.1 Chemical Names & Formulas Monoatomic Ions Remember, an ion is an atom that has gained or lost one or more electrons Cations form when atoms lose electrons Anions form when atoms gain electrons Monoatomic ions are ions formed from a single atom

7.1 Chemical Names & Formulas Naming Monoatomic Ions How do we predict how many electrons an atom likes to lose or gain? Think back to electron configuration and the octet club…. Many atoms like to gain or lose a given number of electrons so that they can have an octet (eight electrons) in their outermost energy level (valence shell) Elements in Group 1 (ns 1 ) like to lose one electron Na sodium Na 1+ a sodium ion Elements in Group 2 (ns 2 ) like to lose two electrons Mg magnesium Mg 2+ a magnesium ion

7.1 Chemical Names & Formulas Naming Monoatomic Ions, cont’d Elements in Group 16 (ns 2 np 4 ) have six valence electrons and like to gain two electrons O oxygen O 2- an oxide ion S sulfur S 2- a sulfide ion Elements in Group 17 (ns 2 np 5 ) have seven valence electrons and like to gain one electron Cl chlorine Cl 1- a chloride ion Br bromine Br 1- a bromide ion Did you notice how the monoatomic anions had a “name change” with the original prefix plus an “ide” ending and that the names of the monoatomic cations did not change?

7.1 Chemical Names & Formulas Naming Monoatomic Ions, cont’d Notice that some non-metal atoms like carbon or silicon in Group 14 (ns 2 np 2 ) do not like to gain or lose electrons. They would rather share electrons and make covalent bonds. Some “other” metals in Group 14 sometimes gain or lose a given number of electrons that do not lead to an octet or “noble-gas” configuration Pb 2+ an lead ( II ) ion (no octet) vs Pb 4+ an lead ( IV ) ion (octet) Sn 2+ tin ( II ) ion (no octet) vs Sn 4+ tin ( IV ) ion (octet)

7.1 Chemical Names & Formulas Naming Monoatomic Ions, cont’d Some transition metals in the d-block as well as some “other” metals in the p-block can generate several different ions Fe 2+ an iron( II ) ion Fe 3+ iron( III ) ion Th 1+ an thallium ( I ) ion Th 3+ an thallium( III ) ion We will deal with these more complex situations after we learn the basics…

7.1 Chemical Names & Formulas Naming Monoatomic Ions, cont’d Please become familiar with the chart on p. 221 in your textbook that lists the charges associated with common monoatomic ions And now let’s look at how to write the name of a binary ionic compound given its chemical formula

7.1 Chemical Names & Formulas Remember, binary ionic compounds are composed of two elements, one metal and one non-metal HHe LiBeBCNOFNe NaMgAlSiPSClAr KCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKr RbSrYZrNbMoTcRuRhPdAgCdInSnSbTeIXe CsBaLuHfTaWReOsIrPtAuHgTlPbBiPoAtRn FrRaLrRfDbSgBhHsMtUunUuuUubUut MetalsMetalloids Non- metals

7.1 Chemical Names & Formulas Binary Ionic Compound two elements - one metal and one non-metal Ionic Compound Metal cation Non-Metal Anion

To identify binary ionic compounds look for: a) 2 elements (“binary”) b) a metal & a non-metal (“ionic”) To name binary ionic compounds: 1)Write the name of the metal (the cation) 2)Write the name of the non-metal (the anion) with the suffix “-ide” 7.1 Chemical Names & Formulas Identifying & Naming Binary Ionic Compounds The subscripts in the chemical formula do not matter when naming this type if the metal involved only forms a single type of cation

Example #1 NaCl

Example #1 NaCl Cation Anion “Sodium” “Chlorine” becomes “Chloride” Sodium Chloride

Example #2 CaBr 2

Example #2 Cation Anion “Calcium” “Bromine” becomes “Bromide” CaBr 2 Calcium Bromide

Example #3 K2OK2O

K2OK2O Cation Anion “Potassium” “Oxygen” becomes “Oxide” Potassium Oxide

Let’s Practice Example: Write the name for the following compounds CaF 2 Na 3 P RbCl SrBr 2

Let’s Practice Calcium fluoride Sodium phosphide Rubidium chloride Strontium bromide Example: Write the name for the following compounds CaF 2 Na 3 P RbCl SrBr 2

7.1 Chemical Names & Formulas Now, let’s try naming ionic compounds that contain a polyatomic ion… Remember, a polyatomic ion is a group of atoms that has gained or lost one or more electrons NO 3 1- a nitrate ion SO 3 2- a sulfite ion SO 4 2- a sulfate ion OH 1- a hydroxide ion NH 4 1+ an ammonium ion PO4 3- a phosphate ion Please note the variety of charges and endings for the names

7.1 Chemical Names & Formulas Polyatomic Ionic Compound compound containing at least one polyatomic ion + Cation + Cation - Polyatomic Anion Polyatomic Ionic Compound OR - Anion - Anion + Polyatomic Cation Polyatomic Ionic Compound + Polyatomic Cation Polyatomic Ionic Compound OR - Polyatomic Anion

7.1 Chemical Names & Formulas COMMON POLYATOMIC IONS Acetate, CH 3 COO -1 or C 2 H 3 O 2 -1 Ammonium NH 4 +1 Bromate, BrO 3 -1 Bromite, BrO 2 -1 Carbonate, CO 3 -2 Carbonite, CO 2 -2 Chlorate, ClO 3 -1 Chlorite, ClO 2 -1 Chromate, CrO 4 -2 Cyanide, CN -1 Dichromate, Cr 2 O 7 -2 Dihydrogen phosphate, H 2 PO 4 -1 Hydrogen carbonate or bicarbonate, HCO 3 -1 Hydrogen phosphate or biphosphate, HPO 4 -2 Hydrogen sulfate or bisulfate, HSO 4 -1 Hydroxide, OH -1 Hypochlorite, ClO -1 Iodate, IO 3 -1 Iodite, IO 2 -1 Nitrate, NO 3 -1 Nitrite, NO 2 -1 Oxalate, C 2 O 4 -2 Perchlorate, ClO 4 -1 Permanganate, MnO 4 -1 Peroxide, O 2 -2 Phosphate, PO 4 -3 Phosphite, PO 3 -3 Silicate, SiO 3 -1 Sulfate, SO 4 -2 Sulfite, SO 3 -2 Your textbook (p. 226) has a similar table of common polyatomic ions

The only polyatomic cation (front-half) is “NH 4 1+ ” All other polyatomic ions are anions (back-half) The subscripts within the polyatomic ion are important they must match exactly with the one on your ion list SO 3 2- a sulfite ion SO 4 2- a sulfate ion NO 2 1- a nitrite ion NO 3 1- a nitrate ion If there are parentheses, the polyatomic ion is inside (ignore the number outside for naming purposes) 7.1 Chemical Names & Formulas Identifying & Naming Polyatomic Ions

7.1 Chemical Names & Formulas Practice Identifying Polyatomic Ions Example: Identify and name the polyatomic ion in each compound NaNO 3 NH 4 Cl Ca(OH) 2 (NH 4 ) 3 PO 4 K 2 CO 3

Practice Identifying Polyatomic Ions Example: Identify and name the polyatomic ion in each compound NaNO 3 NH 4 Cl Ca(OH) 2 (NH 4 ) 3 PO 4 K 2 CO 3 Nitrate Ammonium Hydroxide Ammonium & phosphate Carbonate

Polyatomic ionic compounds have:  More than 2 capital letters (non starting with H)  Contain at least 1 metal & 1 non-metal (unless the compound is made up of two polyatomic ions) To name these compounds:  Write the name of the cation (the metal element name or “Ammonium” for “NH 4 ”)  If the anion is a polyatomic ion, write the polyatomic ion’s name just as it is  If the anion is a single non-metal element, write its name with the suffix “-ide” 7.1 Chemical Names & Formulas Identifying & Naming Polyatomic Ionic Compounds

Example #4 NaNO 3

Example #4 NaNO 3 Cation Polyatomic Anion “Sodium” “Nitrate” Sodium Nitrate

Example #5 K 2 SO 4

Example #5 Cation Polyatomic Anion “Potassium” “sulfate” K 2 SO 4 Potassium sulfate

Example #6 Ca(OH) 2

Example #6 Ca(OH) 2 Cation Polyatomic Anion “Calcium” “hydroxide” Calcium hydroxide

Example #7 (NH 4 ) 2 S

Example #7 Polyatomic Cation Anion “Ammonium” “sulfur” becomes “sulfide” (NH 4 ) 2 S Ammonium sulfide

Let’s Practice Example: Write the name for the following compounds Ca(NO 3 ) 2 Na 3 PO 4 NH 4 ClO K 2 CO 3

Let’s Practice Calcium nitrate Sodium phosphate Ammonium hypochlorite Potassium carbonate Example: Write the name for the following compounds Ca(NO 3 ) 2 Na 3 PO 4 NH 4 ClO K 2 CO 3

7.1 Chemical Names & Formulas Identifying & Naming Ionic Compounds Containing Multivalent Metal Ions If I ask you to bring me the copper chloride off the shelf, you might be confused as to what to bring me. Why? It turns out there are two different copper chlorides, CuCl and CuCl 2. Let’s learn the rules which help us distinguish between CuCl and CuCl 2 as well as other compounds that contain multivalent metal ions…

7.1 Chemical Names & Formulas Identifying & Naming Ionic Compounds Containing Multivalent Metal Ions Multivalent Metal = a metal that has more than one possible cationic charge See p. 221 in the Modern Chemistry TB Type of Metal ChromiumCr 2+ Cr 3+ CobaltCo 3+ CopperCu 1+ Cu 2+ IronFe 2+ Fe 3+ LeadPb 2+ Pb 4+ ManganeseMn 2+ Mn 3+ MercuryHg 2 2+ Hg 2+ ThalliumTh 1+ Th 3+ TinSn 2+ Sn 4+

7.1 Chemical Names & Formulas Identifying & Naming Ionic Compounds Containing Multivalent Metal Ions To distinguish the ions with multiple possible charges, scientists use the Stock system of nomenclature This system uses a Roman numeral to indicate an ion’s charge The Roman numeral is enclosed in parentheses and placed immediately after the metal name Fe 2+ an iron( II ) ion Fe 3+ an iron(III) ion Th 1+ a thallium (I) ion Th 3+ a thallium (III) ion

7.1 Chemical Names & Formulas Identifying & Naming Ionic Compounds Containing Multivalent Metal Ions Please note that metals that form only one type of cation DO NOT get a Roman numeral Examples: Group I Alkali metals do not get Roman numerals Group II Alkaline Earth metals do not get Roman numerals Silver and Gold do not get Roman numerals Aluminum does not get a Roman numeral Zinc does not get a Roman numeral

To name these compounds:  Write the name of the multivalent metal element (cation)  Write the name of the anion (element name with “-ide” or polyatomic ion name)  Determine the total negative charge  Total negative charge = total positive charge for all neutral compounds  Determine the charge on each metal atom  Write the charge in roman numerals in parenthesis after the metal’s name* * only if the metal forms multiple cations!!!! 7.1 Chemical Names & Formulas Identifying & Naming Ionic Compounds Containing Multivalent Metal Ions

Example #8 CuCl

Example #8 CuCl Cation Anion “Copper” “Chlorine” becomes “Chloride” Copper Chloride

Example #8 CuCl Cation Anion “Copper” “Chlorine” becomes “Chloride” Copper Chloride Chloride has a –1 charge -1 charge * 1 ion = -1 A –1 charge needs a +1 charge Therefore, copper must be +1 (I)(I)

Example #9 Fe 2 (CO 3 ) 3

Example #9 Fe 2 (CO 3 ) 3 Cation Polyatomic Anion “Iron” “Carbonate” Iron carbonate

Example #9 Fe 2 (CO 3 ) 3 Cation Polyatomic Anion “Iron” “Carbonate” Iron carbonate Carbonate has a –2 charge -2 charge * 3 ions = -6 A –6 charge needs a +6 charge and there are 2 iron ions Therefore, iron must be +3 ( III )

Let’s Practice Example: Write the name for the following compounds PbCl 2 PbCl 4 MnO Mn 2 O 3

Let’s Practice Lead ( II ) chloride Lead ( IV ) chloride Manganese ( II ) oxide Manganese ( III ) oxide Example: Write the name for the following compounds PbCl 2 PbCl 4 MnO Mn 2 O 3

7.1 Chemical Names & Formulas Identifying & Naming Binary Molecular Compounds Remember molecular compounds are formed from two non-metals that share electrons Non metal Non metal Non metal Non metal Covalent compound A different system is used to name molecular compounds than ionic compounds

These compounds have:  2 elements (“binary”)  Both non-metals (“covalent”) To name these compounds:  Write the name of the first element with the prefix indicating the number of atoms (except don’t use “mono-”)  Write the name of the second element with the prefix indicating the number of atoms (including “mono-”) and the suffix “ide” 7.1 Chemical Names & Formulas Identifying & Naming Binary Molecular Compounds

See Table 3 p. 228 in Modern Chemistry TB for the list of prefixes used to name molecular compounds Number of AtomsPrefix 1mono- 2di- 3tri- 4tetra- 5penta- 6hexa- 7hepta- 8octa- 9nona- 10deca-

Let’s Practice Example #10 P2O5P2O5

P2O5P2O5 Phosphorus Oxygen 2 = “di-” 5 = “penta-” Use “-ide” Diphosphorus pentaoxide

Let’s Practice Example #10 SiO 2

Let’s Practice Example #10 Silicon Oxygen Don’t use “mono-” on first element 2 = “di-” Use “-ide” SiO 2 Silicon dioxide

Let’s Practice Example: Write the name for the following compounds CO 2 N2O4N2O4 P 4 O 10 CO

Let’s Practice Carbon dioxide Dinitrogen tetraoxide Tetraphosphorus decaoxide Carbon monoxide Example: Write the name for the following compounds CO 2 N 2 O 4 P 4 O 10 CO

Nomenclature Summary Naming Chemical Formulas Starts with a metal or NH4 2 capital letters = Binary Ionic More than 2 elements = Polyatomic Ionic Does not contain a metal = Binary Covalent compound

Mixed Practice Example: Write the name for the following compounds SO 3 K 3 PO 4 Cu(OH) 2 PF 5 Na 2 O Sulfur trioxide Potassium phosphate Copper ( II ) hydroxide Phosphorus pentafluoride Sodium oxide

7.1 Chemical Names & Formulas / Identifying & Naming Acids Acids are molecular compounds that generate hydrogen ions in solution (HCl → H + + Cl - ) They can be classified as binary acids or oxyacids Binary Acids consist of two elements, usually hydrogen and one of the halogens Ex: HCl Oxyacids contain hydrogen, oxygen, and a third element Ex: H 2 SO 4 Many polyatomic ions are produced by the loss of hydrogen ions from oxyacids (H 2 SO 4 vs SO 4 2- )

These identify these compounds:  They start with “H” (more than 1 “H” is OK, too).  They do not contain oxygen To name these compounds:  Use “hydro____ic acid”  Fill in the blank with the anion’s name without the last syllable 7.1 Chemical Names & Formulas / Identifying & Naming Binary Acids

Example #1 HBr

Example #1 HBr Hydrogen cation Bromine It’s an acid No oxygen Use “hydro___ic” Hydrobromic acid

To identify these compounds:  They start with “H” (more than 1 “H” is OK, too).  They do contain oxygen To name these compounds:  Use “___ic acids” for “-ate” anions  Use “___ous acids” for “-ite” anions 7.1 Chemical Names & Formulas / Identifying & Naming Oxyacids Do not use “hydro” with these…the word “acid” is how you know it begins with hydrogen, not “hydro-”

Example #2 H 2 SO 3

Example #2 Hydrogen cation Sulfite ion It’s an acid “-ite” ion Use “___ous” acid H 2 SO 3 Sulfurous acid

Example #3 H 2 SO 4

Example #3 Hydrogen cation Sulfate ion It’s an acid “-ate” ion Use “___ic” H 2 SO 4 Sulfuric acid

Let’s Practice Example: Write the name for the following compounds HCl HNO 3 H2SH2S H 3 PO 3

Let’s Practice Hydrochloric acid Nitric acid Hydrosulfuric acid Phosphorous acid Example: Write the name for the following compounds HCl HNO 3 H 2 S H 3 PO 3