Presentation on theme: "Naming Compounds and Writing Formulas"— Presentation transcript:
1 Naming Compounds and Writing Formulas Developed By: Ms. Michelle BurokerModified & Expanded By: Dr. Rick Moleski
2 5 Types of Chemical Compounds (Based on Type of Bond)Binary ionic - metal ion – nonmetal ionTernary ionic - at least one ion is a polyatomic ion (either cation or anion)Binary molecular - two nonmetalsBinary acid - H +1 – nonmetalTernary acid - H +1– Polyatomic ion
3 Naming Binary Ionic Compounds STEP 1: Name the first ion (cation)If the first ion is a transition element other than zinc, cadmium, or silver, you must use a Roman Numeral with the name – we’ll discuss this later.You check the Periodic Table for the charge-Column 1 = 1 valence electron = +1 chargeColumn 2 = 2 valence electrons = +2 chargeColumn 13 = 3 valence electrons = + 3 chargeSTEP 2: Name the second ion (anion) changing the suffix to –ide.
4 Name the metal element = cation ExamplesNaClName the metal element = cationSodiumChlorideCaOName the nonmetal by adding the suffix –ide to the root element nameCalciumOxideAl2S3AluminumSulfideMgI2MagnesiumIodide
5 Notice – metal and nonmetal. What about the transition metals and using Roman Numerals? How does that work? Let’s see.Notice – metal and nonmetal.FeOName the first ion. Since the first ion is a transition element, you must use a Roman Numeral to represent the charge. Exceptions Zn (+2) Ag (+1) Cd (+2)Iron (II) OxideHow do you know the charge?Deductive reasoning.All compounds are neutral.Oxygen has a -2 charge (Column 16, group 6A)Therefore ….. Iron must have a +2 charge since there is one iron and one oxygen. Iron gets a Roman Numeral II.
6 Name the first ion. Since it is a transition metal, you must use a Roman Numeral. Which Roman Numeral? The Roman Numeral is the same as the charge of the ion.How do you find the charge?Deductive reasoning!All compounds are neutralSulfur has a -2 charge (group 6A)There are two coppers.Therefore each copper must have a +1 charge for all ions to be neutralCu2SCopperISulfide
7 Another Example: MnO2Name the first ion. Since it is a transition metal, you must use a Roman Numeral.How do you determine the Roman Numeral?It is the same as the charge.What is the charge of Mn?All compounds are neutral.Oxygen (group 16) has a -2 charge.There are two oxygens and one Mn.Therefore Mn must have a +4 charge for this compound to be neutral.ManganeseIVoxide
8 So why must we use Roman Numerals with transition elements? The metals in groups 1A, 2A, and 3A have single, definite charges or referred to as being monovalentColumn 1, Group 1A metals have a +1 charge.Column 2, Group 2A metals have a +2 charge.Column 13, Group 3A metals have a +3 charge.Transition metals may have multiple charges – usually two different positive charges. They are referred to as being multivalentFor example, there are two copper oxide compounds:which is which?We can’t just say Copper oxide. Which one of these is Copper oxide? We must distinguish these by using a Roman NumeralCu2O and CuO
9 The solution lies with the negative ion or nonmetal’s charge which are always related back to the number of valence electrons and hence their oxidation number:Column 17, group 7A has a -1 charge (due to 7 valence e-)Column 16, group 6A has a -2 charge (due to 6 valence e-)Column 15, group 5A has a -3 charge (due to 5 valence e-)Given CuO we know that there is a -2 charge per O atom and since there is only one O atom the total negative charge is -2 and must be offset by a +2 charge; because there is only copper atom it has to have a +2 charge or oxidation number giving us the namecopper (II) oxideFrom a bonding perspective, the -2 charge of the O atom represents the acquisition of 2 electrons. These two electrons came from the copper atom and would represent the lose of 2 electrons
10 The other form of “copper oxide” has the formula Cu2O To determine its name we use the same approach:Oxygen has a -2 charge per atom and since there is only one atom the total negative charge is -2 (12 charge/ atom x 1 atom = -2)Therefore the offsetting positive charge has to have a total positive charge of +2 and since this charge is from 2 atoms of copper, each has a +1 charge (+2 total charge ÷ 2 atoms = +1 charge per atom)This gives us an charge or oxidation number of +1 and a Roman numeral of (I)Name: copper (I) oxide
11 You need to remember the charges for these!!! There are three transition elements which do not require a Roman Numeral because they have single definite charges.Zinc – Zn+2Cadmium – Cd+2Silver – Ag+1You need to remember the charges for these!!!No Roman Numerals needed for these.Ag2OName the first ion.Name the second ion changing the suffix to –ide.SilveroxideZnCl2Name the first ion.ZincchlorideName the second ion changing the suffix to –ide.
12 Sometimes you will see the transition elements named using common/traditional names. The common names use the Latin derivative of the element’s name with a suffix of either –ous or –ic.The –ous suffix name corresponds with the smaller charge.The –ic suffix name corresponds with the larger charge.With the traditional names using the different suffixes, you had to memorize both the name and the charges- not so with the Stock system since the Roman numeral tells you the charge.Remember Transition Metals named with Roman Numerals involve stock names.
13 Some Examples Stock name Common Name Copper I Cuprous Copper II Cupric Iron IIFerrousIron IIIFerricLead (II)PlumbousLead (IV)plumbic
14 How do you write formulas for binary ionic compounds given the name? Three simple steps:Write the symbol and charge of each ionBalance the charges by adjusting number of ionsBased on the ratio apply the necessary subscriptsMagnesium chlorideWrite the symbol and charge of each ion.You need a second Cl-1 to balance the chargesThe number of each ion (their ratio) tells you the subscripts for eachMg Cl-1Cl-1MgCl2If only 1 atom then you omit that subscript
15 FeBr3 More examples: Iron (III) bromide Write the symbol and charge of each ion. The charge of the iron is provided by the Roman Numeral.Br -1Br -1Balance the charges by adjusting the number of ions; this becomes the subscripts. The subscripts tell how many of each ion is needed to balance the compound.FeBr3You’ll need three bromide ions to balance the charge (+3) of one iron (III) ion.
16 Al2S3 Write the symbol and charge of each ion. Balance the charges by supplying subscripts.In this case the charges do not evenly divide into each other. You must find the least common multiple (LCM). SIXAluminum SulfideAl S-2S-2Al+3S-2How many aluminums are needed to arrive at a +6 charge?2Al2S3How many sulfurs are needed to arrive at a -6 charge?3
17 Naming Ternary Compounds These compounds contain at least one polyatomic ion.What is a polyatomic ion?Let’s look at the name to try to understand.It is an ion – that means it has a charge.It is polyatomic – that means it is made of more than one atom.Let’s look at some examples of polyatomic ions
18 This ion is composed of one carbon and three oxygens and the entire group has a charge of -2. carbonatePolyatomic ion – Group of covalently bonded atoms that carry an electrical charge and act as a unit during reactions, that is, the atoms stay bonded together. More examples:MnO4-1PermanganateSO4-2SulfatePO4-3PhosphateC2H3O2-1AcetateSO3-2SulfiteOH-1HydroxideClO4-1PerchlorateNO3-1NitrateClO3-1ChlorateNO2-1NitriteClO2-1ChloriteNH4+1AmmoniumClO-1HypochloriteYou need to learn these!!!
19 How do you recognize Ternary Ionic Compounds? You see more than two element symbolized in the chemical formula Composed of two ions in which at least one is a polyatomic ion. There is only one common positive polyatomic ion, ammonium (NH4+1), that forms a compound
20 Na2CO3 How do you name Ternary Ionic Compounds? EASY! PIECE OF CAKE! NO PROBLEM!1) Name the first ion.2) Name the second ion.When you look at this compound you should recognize that this is NOT binary. There are THREE elements present. When you see this, immediately look for a polyatomic ion. Carbonate is present here.Na2CO3Name the first ion.SodiumcarbonateName the second ion.
21 A few more examples:Fe(OH)3step 1- Name the first ion.Iron(III)hydroxideRemember that iron requires a Roman Numeral since it is a transition element. What Roman Numeral should be used?Since there are 3 OH groups, each with a -1 charge, the charge of the iron must be +3 for the compound to be neutralThe Roman Numeral comes from the charge of the ion. How do you find the charge of the iron?You know two things:All compounds are neutral.You know the charge of OH (-1)step 2- Name the polyatomic ion.
22 step 1- Name the first ion. NH4Clstep 2- Name the second ion.AmmoniumchlorideNotice that since the second ion is a nonmetal as in binary ionic compounds, the suffix of the nonmetal changes to –ide.step 1- Name the first ion.(NH4)3PO4Ammoniumphosphatestep 2- Name the second ion.
23 ONE more example:Cu2SO4step 1- Name the first ion.You should realize that you need a Roman Numeral since copper is a transition metal.The Roman Numeral is the same as the charge.What is the charge?Working backwards - the charge of sulfate is a -2 per polyatomic ion and there’s only 1 giving us a total of -2.The plus charge must offset the -2 giving us a total plus charge of+2 Since there are two coppers, the charge per copper ion must be +1.Copper(I)sulfatestep 2- Name the second ion.
24 How do you write formulas for Ternary Ionic Compounds? Very much like writing formulas for Binary Ionic Compounds.Three steps:Write the formulas/symbols of each ion.Balance the charges by adjusting the number of ionsFrom the resulting ratio apply subscripts equal to the number of ions.If a subscript is needed for a polyatomic ion, it must be put in parentheses with the subscript on the outside.
25 Al(NO3)3 Aluminum nitrate First, you can tell from the name that there is a polyatomic ion present (nitrate). Remember that all binary ionic compounds have suffixes of –ide.Al NO3-1Al(NO3)3Write the formula/symbol and charge of each ion.Balance the charges by adjusting the number of ions and those numbers (ratio) become the subscripts in the formula.Since Al is +3 and NO3 is -1, you need a total of 3NO3-1 to balance one Al+3You will need a subscript of 3 for NO3-1; you need to put this in parentheses with the 3 outside.
26 Ca3(PO4)2 Pb(C2H3O2)4 Lead (IV) acetate Write the formula/symbol and charge of each ion.Pb C2H3O2-1Balance the charges by adjusting the number of ions and this number becomes the subscripts. Since Pb is +4 and C2H3O2 is -1, you will need 4 C2H3O2-1 to balance 1Pb+4Pb(C2H3O2)4Write the formula/symbol and charge of each ion.Calcium phosphateCa PO4-3Balance the charges to determine subscripts. Use the LCM of 6. Since Ca is +2 and PO4 is a -3, you will need 3 Ca+2 to balance 2 PO4-3Ca3(PO4)2
27 Naming Binary Molecular Compounds using Traditional Nomenclature These compounds consist of two non-metals and to name them, you need to know the following prefixes:1Mono-2Di-3Tri-4Tetra-5Penta-6Hexa-7Hepta-8Octa-9Nona-10Deca-
28 The Rules….The first nonmetal only gets a numeric prefix when there is more than one. No prefix if there is only one.The second element always gets a numeric prefix and always has a suffix of -ide
29 CO2 CO Carbon dioxide Carbon monoxide N2O4 Dinitrogen tetraoxide H2O Dihydrogen monoxideCCl4Carbon tetrachlorideName the first element. Since there is only one, no prefix is needed. The second element always gets a prefix and a suffix of –ide.examples are CO2 and COName the first element. Since there are two present, the prefix “di” is needed. The second element always gets a prefix and a suffix of –ide.examples are N2O4 and H2OWhy do we use the prefix tetra for the name of CCl4?
30 Writing Formulas for Binary Molecular Compounds using the Traditional Nomenclature Sytem Very easy to do!!! The prefixes tell you how to write the formulas. example diphosphorus pentoxideRemembering di = 2 and penta = 5, we getP2O5Notice that we drop the a from penta when adding to oxide
31 SiO2 P2Cl5 Silicon dioxide Diphosphorous pentachloride Silicon and oxygen are both nonmetals.The lack of a prefix on silicon means that there is only ONE silicon.The prefix “di” in front of oxide means that there are TWO oxygens.Silicon dioxideSiO2Diphosphorous pentachloridePhosphorous and chloride are both nonmetals.The prefix “di” means that there are TWO atoms of phosphorous covalently bonded to the chlorinesThe prefix “penta” before chlorine means that there are five chlorines.P2Cl5
32 Nitrogen and oxygen are both nonmetals. The lack of a prefix on nitrogen means only ONE nitrogen.The prefix “mono” on oxygen indicates ONE oxygen.Nitrogen monoxideNOBut wait these nonmetal molecular compounds can be written using the Stock System
33 Naming Molecular Compounds using the Stock System This system uses Roman Numerals that indicate the oxidation number of the first nonmetal in the formula. This is similar to what we did with the transition metals; for example P2O5step 1- we assign a charge value of -2 per Oxygen atomstep 2- we calculate the total negative charge -2 x 5 = -10step 3- we know that 2 phosphorus atoms contributed to an offsetting +10 giving us a +5 charge per P atomstep 4- write the name of the first element followed by the Roman numeral for 5 in parenthesisstep 5- use the –ide form of the second nonmetal’s namephosphorus (V) oxide
34 Writing Nonmetal Molecular Formulae using Stock System Since the name tells you the charge per atom of the first nonmetal, you follow these steps using sulfur (VI) oxide as our example:step 1- determine the charge of the second nonmetal from its position on the Periodic Table- -2 charge/O atom (column 17)step 2- figure out how many oxygen atoms are needed to equal a charge of -6 since you know that sulfur is a +6; 3 Ostep 3- from the ratio write the formula; 1S:3O = SO3Another example: phosphorus (V) oxide Let’s see what you can do
35 step 1- using the -2 oxidation number (charge) for an oxygen atom we know that it will not go into 5 as a whole number which is needed since atoms do not exist as fractional entitiesstep 2- the remedy is to find the LCM (lowest common multiple) of both +5 (from the Roman numeral in the name) and -2 (found in the previous step) – lcm is found by multiplying the two charge numbers without regard for sign together 5 x 2 = 10step 3- divide 10 by both charges resulting in the ratio of atomsP: 10 ÷ 5 = O: 10 ÷ 2 = 5Ratio 2P:5Ostep 4- write the formula using the ratio as the required subscriptsP2O5
36 Naming Binary AcidsRemember that acids always begin with an “H” in their formula and are aqueous solutions So, what is a binary acid? Binary Acids are those which contain hydrogen and a non-metal element. Naming them requires a prefix and a suffix added to the root of the nonmetal element and the word “acid” added afterwards
37 Stem or root of nonmetal PrefixSuffix-icAcidHydro-< NM >HCl is a binary acid – hydrogen + nonmetal chlorineHClHydrochloricAcidHIHydroiodicAcidH2SHydrosulfuricAcid
38 Writing Formulas For Binary Acids The obvious pattern of the name tells you that it is a binary acid. Hydro<NM>ic Acid.Therefore, you know that the acids begins with hydrogen and contains a nonmetal which you can identify between the “Hydro” and the “ic”To arrive at the formula, you “pretend” that hydrogen is +1 and using the normal charge of the nonmetal, balance the formula by adjusting their number of atoms thereby determining the subscripts.
39 H3P Hydrophosphoric acid The name tells you that it is definitely a binary acid. How? The hydro prefixstep 1- you find the oxidation number for phosphorus from the Periodic Table (P = -3)step 2- determine how many “H” you need at a “+1” to equal -3; answer 3step 3- write the formula using the above ratio for the number of each elementH P-3H3PRemember that the P has a -3 charge because it is in Column 15 (group 5A) thereby signifying 5 valence electrons and a -3 charge when stable
42 Naming Ternary AcidsThese compounds begin with hydrogen since they are “acids”.Attached to the hydrogen is a polyatomic ionHydrogen – polyatomic ionexamples:H2SO4HNO3H2CO3
43 -ic acid How are Ternary Acids named? There are two categories of naming depending on the suffix of the polyatomic ion.First Category: If the polyatomic ion has a suffix of –ate, use the following pattern:suffix-icacidRoot of polyatomic ion +Ternary Acid – contains the polyatomic ion chlorate (suffix= ic) becoming chloricHClO3ChloricAcidTernary Acid – contains the polyatomic ion nitrate (suffix= ic) becoming nitricHNO3NitricAcidH2SO4SulfuricAcidTernary Acid – contains the polyatomic ion sulfate (suffix= ic) becoming sulfuric
44 Second Category: If the polyatomic ion has a suffix of –ite, use the following pattern: Root of polyatomic ion +-ousacidTernary acid contains polyatomic ion, nitrite (-ite suffix) becoming nitrous.HNO2NitrousacidHClO2ChlorousacidTernary acid contains polyatomic ion, chlorite (-ite suffix) becoming chlorous.SulfurousacidTernary acid contains polyatomic ion, sulfite (-ite suffix) becoming sulfurous.H2SO3
45 Writing Formulas for Ternary Acids First, a ternary acid is easy to distinguish from a binary acid.ALL binary acids have the prefix “hydro-”.Most Ternary acids have the prefix “hydro-” but a few do like HCN which is hydrocyanic acid- the exceptions are simply memorized.Acetic acidThis is an acid, but NOT a binary acid; it’s TernaryWill begin with an “H” followed by the corresponding polyatomic ionThe “-ic” suffix in the acid name tells you that the polyatomic ion must have a “-ate” suffix – acetate.To write the formula, pretend that hydrogen is +1 and balance the charges.H+1 C2H3O2-1HC2H3O2
46 HClO H3PO4 Hypochlorous acid This is a Ternary acid (does not begin with “hydro-”; although “hypo” it’s not the same).H ClO-1The “-ous” suffix indicates that the polyatomic ion in this acid has a suffix of “-ite” - hypochloriteHClOPretend that hydrogen is +1 and balance the charges giving you their combining ratio.This is a Ternary acid (does not begin with “hydro-”).Phosphoric acidH PO4-3The “-ic” suffix indicates that the polyatomic ion in this acid has a suffix of “-ate” - phosphateH3PO4Pretend that hydrogen is +1 and balance the charges giving you their combining ratio .
47 There You Have It – That’s All Folks NOW for the Secret to Success PRACTICEPRACTICE PRACTICEandSTILL MORE PRACTICEThat’s All Folks
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