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Naming Compounds and Writing Formulas

Naming Compounds and Writing Formulas. Developed By: Ms. Michelle Buroker Modified & Expanded By : Dr. Rick Moleski. 5 Types of Chemical C ompounds (Based on Type of Bond) Binary ionic - metal ion – nonmetal ion

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Naming Compounds and Writing Formulas

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  1. Naming Compounds and Writing Formulas Developed By: Ms. Michelle Buroker Modified & Expanded By: Dr. Rick Moleski

  2. 5 Types of Chemical Compounds (Based on Type of Bond) Binary ionic - metal ion – nonmetal ion Ternary ionic - at least one ion is a polyatomic ion (either cation or anion) Binary molecular- two nonmetals Binary acid - H +1 – nonmetal Ternary 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 charge • Column 2 = 2 valence electrons = +2 charge • Column 13 = 3 valence electrons = + 3 charge STEP 2: Name the second ion (anion) changing the suffix to –ide.

  4. Examples NaCl Name the metal element = cation Sodium Chloride CaO Name the nonmetal by adding the suffix –ide to the root element name Calcium Oxide Al2S3 Aluminum Sulfide MgI2 Magnesium Iodide

  5. What about the transition metals and using Roman Numerals? How does that work? Let’s see. Notice – metal and nonmetal. FeO Name the first ion. Since the first ion is a transitionelement, you must use a Roman Numeral to represent the charge. Exceptions Zn (+2) Ag (+1)Cd(+2) Iron (II) Oxide How 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 neutral Sulfur has a -2 charge (group 6A) There are two coppers. Therefore each copper must have a +1 charge for all ions to be neutral Cu2S Copper I Sulfide

  7. Another Example: MnO2 Name 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. Manganese IV oxide

  8. So why must we use Roman Numerals with transition elements? The metals in groups 1A, 2A, and 3A have single, definite chargesor referred to as being monovalent Column 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 multivalent For 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 Numeral Cu2O 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 name copper (II) oxide From 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. There are three transition elements which do not require a Roman Numeral because they have single definite charges. Zinc – Zn+2 Cadmium – Cd+2 Silver – Ag+1 You need to remember the charges for these!!! No Roman Numerals needed for these. Ag2O Name the first ion. Name the second ion changing the suffix to –ide. Silver oxide ZnCl2 Name the first ion. Zinc chloride Name 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

  14. How do you write formulas for binary ionic compounds given the name? • Three simple steps: • Write the symbol and charge of each ion • Balance the charges by adjusting number of ions • Based on the ratio apply the necessary subscripts Magnesium chloride Write the symbol and charge of each ion. You need a second Cl-1 to balance the charges The number of each ion (their ratio) tells you the subscripts for each Mg+2 Cl-1 Cl-1 MgCl2 If only 1 atom then you omit that subscript

  15. More examples: Iron (III) bromide Write the symbol and charge of each ion. The charge of the iron is provided by the Roman Numeral. Fe+3 Br -1 Br -1 Br -1 Balance 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. FeBr3 You’ll need three bromide ions to balance the charge (+3) of one iron (III) ion.

  16. 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). SIX Aluminum Sulfide Al+3 S-2 S-2 Al+3 S-2 How many aluminums are needed to arrive at a +6 charge? 2 Al2S3 How 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. CO3-2 carbonate Polyatomic 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: MnO4-1 Permanganate SO4-2 Sulfate Phosphate PO4-3 C2H3O2-1 Acetate SO3-2 Sulfite OH-1 Hydroxide ClO4-1 Perchlorate NO3-1 Nitrate ClO3-1 Chlorate NO2-1 Nitrite ClO2-1 Chlorite NH4+1 Ammonium ClO-1 Hypochlorite You 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. 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. Na2CO3 Name the first ion. Sodium carbonate Name the second ion.

  21. A few more examples: Fe(OH)3 step 1- Name the first ion. Iron hydroxide Remember that iron requires a Roman Numeral since it is a transition element. What Roman Numeral should be used? (III) Since there are 3 OH groups, each with a -1 charge, the charge of the iron must be +3 for the compound to be neutral • The 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. NH4Cl step 2- Name the second ion. chloride Ammonium Notice 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)3PO4 Ammonium phosphate step 2- Name the second ion.

  23. ONE more example: Cu2SO4 step 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. sulfate Copper (I) step 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 ions • From 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. 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+3 NO3-1 Al(NO3)3 Write 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+3 You will need a subscript of 3 for NO3-1;you need to put this in parentheses with the 3 outside.

  26. Lead (IV) acetate Write the formula/symbol and charge of each ion. Pb+4C2H3O2-1 Balance 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+4 Pb(C2H3O2)4 Write the formula/symbol and charge of each ion. Calcium phosphate Ca+2 PO4-3 Balance 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 PO4-3 Ca3(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:

  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 alwaysgets a numeric prefix and always has a suffix of -ide

  29. CO2 Carbon dioxide CO Carbon monoxide N2O4 Dinitrogentetraoxide H2O Dihydrogen monoxide CCl4 Carbon tetrachloride Name 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 CO Name 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 areN2O4 and H2O Why 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 diphosphoruspentoxide Remembering di = 2 and penta = 5, we get P2O5 Notice that we drop the a from penta when adding to oxide

  31. 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 dioxide SiO2 Diphosphorouspentachloride Phosphorous and chloride are both nonmetals. The prefix “di” means that there are TWO atoms of phosphorous covalently bonded to the chlorines The 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 monoxide NO But 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 P2O5 step 1- we assign a charge value of -2 per Oxygen atom step 2- we calculate the total negative charge -2 x 5 = -10 step 3- we know that 2 phosphorus atoms contributed to an offsetting +10 giving us a +5 charge per P atom step 4- write the name of the first element followed by the Roman numeral for 5 in parenthesis step 5- use the –ideform of the second nonmetal’s name phosphorus (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 O step 3-from the ratio write the formula; 1S:3O = SO3 Another 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 entities step 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 = 10 step 3- divide 10 by both charges resulting in the ratio of atoms P: 10 ÷ 5 = 2 O: 10 ÷ 2 = 5 Ratio 2P:5O step 4- write the formula using the ratio as the required subscripts P2O5

  36. Naming Binary Acids Remember 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 Prefix Suffix -ic Acid < NM > Hydro- HCl is a binary acid – hydrogen + nonmetal chlorine HCl Acid Hydro chlor ic Hydro iod ic Acid HI Hydro sulfur ic Acid H2S

  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. Hydrophosphoric acid The name tells you that it is definitely a binary acid. How? The hydroprefix step 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; answer3 step 3- write the formula using the above ratio for the number of each element H+1 P-3 H3P Remember 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

  40. Let’s Practice – Reality Check Ca(OH)2 Calcium hydroxide SO2 Sulfur dioxide (NH4)3PO4 Ammonium phosphate Co2(CO3)3 Cobalt (III) carbonate HBr Hydrobromic acid Ternary Ionic Binary molecular Ternary Ionic Ternary Ionic Binary acid

  41. Potassium acetate KC2H3O2 Cadmium nitrate Cd(NO3)2 Aluminum oxide Al2O3 Hydrosulfuric acid H2S Difluorine trioxide F2O3 Ternary Ionic Ternary Ionic Binary Ionic Binary acid Binary molecular

  42. Naming Ternary Acids • These compounds begin with hydrogen since they are “acids”. • Attached to the hydrogen is a polyatomic ion • Hydrogen – polyatomic ion • examples: • H2SO4 • HNO3 • H2CO3

  43. 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 -ic acid Root of polyatomic ion+ Ternary Acid – contains the polyatomic ion chlorate (suffix= ic) becoming chloric ic HClO3 Chlor Acid Ternary Acid – contains the polyatomic ion nitrate(suffix= ic) becoming nitric ic Nitr Acid HNO3 Ternary Acid – contains the polyatomic ion sulfate(suffix= ic) becoming sulfuric ic Sulfur Acid H2SO4

  44. Second Category:If the polyatomic ion has a suffix of –ite, use the following pattern: suffix Root of polyatomic ion+ -ous acid Ternary acid contains polyatomic ion, nitrite (-ite suffix) becoming nitrous. HNO2 acid Nitr ous Chlor ous acid Ternary acid contains polyatomic ion, chlorite (-ite suffix) becoming chlorous. HClO2 Ternary acid contains polyatomic ion, sulfite (-ite suffix) becoming sulfurous. Sulfur ous acid 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 acid This is an acid, but NOT a binary acid; it’s Ternary Will begin with an “H” followed by the corresponding polyatomic ion The “-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 C2H3O2-1 HC2H3O2

  46. Hypochlorous acid This is a Ternary acid (does not begin with “hydro-”; although “hypo” it’s not the same). H+1ClO-1 The “-ous” suffix indicates that the polyatomic ion in this acid has a suffix of “-ite” - hypochlorite HClO Pretend that hydrogen is +1 and balance the charges giving you their combining ratio. This is a Ternary acid (does not begin with “hydro-”). Phosphoric acid H+1 PO4-3 The “-ic” suffix indicates that the polyatomic ion in this acid has a suffix of “-ate” - phosphate H3PO4 Pretend that hydrogen is +1 and balance the charges giving you their combining ratio .

  47. There You Have It – NOW for the Secret to Success PRACTICE PRACTICE PRACTICE and STILL MORE PRACTICE That’sAll Folks

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