Chemical Names & Formulas

Chemical Names & Formulas Name: Period: Date: I. WRITING IONIC FORMULAS 1. are formed by two ions of opposite charge ( are + and are -) and that they are held together by a relatively weak attraction between the ions. 2. KEY IDEA: and elements will combine in such a ratio that there will be a net charge of, forming a ionic compound. 3. Care must be taken that subscripts are correct Ex: NaCl vs. CaCl 2 4. Why does the chlorine have a subscript of 2 in one chemical formula but not in the other? Look at the ion charges! o Sodium is and chloride is A +1 and a -1 charge form an ionic compound with a zero charge! o Calcium is and chloride is NOW ions are needed in order to form a neutral compound 5. The ratio by which elements combine in order to form ionic compounds can often be predicted by using the (CHARGES) of the ions that each element in the compound forms. 6. All IONIC compounds are. So the algebraic sum of the charges has to equal! Ex: Aluminum sulfate has the following chemical formula: Al 2 (SO 4 ) 3 A chemical formula for this ionic compound shows that Al +3 ions and SO -2 4 ions are needed in order to form a neutral compound. 1

7. REMEMBER- Rules for Assigning Oxidation Numbers (charges): 8. Examples of Forming Ionic Compounds Example #1: Write a formula for aluminum chloride. What are the charges of the ions? and What do the charges mean? Aluminum electrons Chlorine electron How is aluminum chloride formed? Use electron-dot formulas to illustrate the formation of ionic bonds involving Al and Cl. It takes chlorine atoms to gain the electrons that aluminum atom can donate. When this transfer occurs, 1 will be formed and three will be formed. These particles will all be held together by the electrostatic charges. The formula is. Think of writing an ionic formula as looking for a lowest possible ratio of positive and negative ions that need to combine in order to form a neutral compound! 2

Example #2: Write a formula for sodium sulfide. What are the charges of the ions? and What is the ratio or combination that these ions must form in order to form a NEUTRAL compound? sodium ions and sulfide ion Write the formula for sodium sulfide: 9. Rules for writing ionic formulas: Ionic compounds are usually created by joining a and a Write the symbol for the positive ion ( ) first, following by the negative ion ( ) The subscript 1 is understood when subscript is present and is not written Use parentheses around when adding additional subscripts. o PROTECT POLYATOMICS WITH PARENTHESES!! Use the criss-cross method- the NUMBERS of the positive and negative ions can be crossed over to give the correct subscripts to the opposite ion. Ex #1: What is the formula of the compound formed by the ions of magnesium and bromine? o Ions = Mg +2 and Br -1 o Formula = Mg Br 2 Ex #2: Aluminum sulfide (use the criss-cross method) o Ions = o Formula = Ex #3: Magnesium oxide o Ions = o Formula = We must reduce this to the lowest terms! The final answer is 3

Ex #4:Sodium peroxide polyatomic- NO parentheses and NO reduction o Ions = o Formula = NO REDUCTION -This is the correct formula for this compound since we cannot reduce a subscript which is already set as a part of the original ion! Ex #5: Copper II sulfate polyatomic- NO parentheses and reduction o Ions = o Formula = Ex #6: Calcium nitrate polyatomic- PROTECT with PARENTHESES You cannot alter the that come with polyatomic ions, we use! o Ions = o Formula = Note: NEVER use around ions (Na, Li, Fe, Cu, etc). Only ions (SO 4, MnO 4, NH 4, PO 3, etc.) will ever require the use of parentheses. II. NAMING IONIC COMPOUNDS: 1. Rules: a. charged ion name comes b. charged ion name comes c. Ions with than one charge/oxidation state, you have to figure out the charge and use the correct! 4

Ex: FeO Determine the charge of the anion (neg. ion) o Oxide s charge is So Fe has to have a charge because FeO is a NEUTRAL compound! Ions have to be: and So it is Ex: Fe 2 O 3 Determine the charge of the anion (neg. ion) o Oxide s charge is -2 and you have 3 ions for a total charge of -6 for the anions. So the 2 Fe ions have to have a total charge of +6 since Fe 2 O 3 is a NEUTRAL compound. Ions have to be: and So it is III. WRITING MOLECULAR FORMULAS 1. Chemical formula for a molecular compound is called a molecular formula 2. = formula showing the types and numbers of atoms combined in a single molecule of a molecular compound Molecular compounds are usually 3. tell you what the will be! Ex: Carbon monoxide Ex: Carbon dioxide Ex: Dinitrogen trioxide Prefixes: 1 Mono- 2 Di- 3 Tri- 4 Tetra- 5 Penta- 6 Hexa- 7 Hepta- 8 Octa- 9 Non- 10 Deca- 5

IV. NAMING MOLECULAR COMPOUNDS 1. Rules for naming molecular compounds: a. A prefix is used with the name of the FIRST element ONLY if there is more than one atom of that element is present. b. The second element is named by combining a prefix and changing the ending to Ex: NO is called Ex: N 2 0 is called 2. Hints to use when molecular and ionic compounds are on the same worksheet/test: Determine if the compound is molecular or ionic. Molecular compounds ONLY contain. Ionic compounds ONLY contain and. Compounds that contain ammonium ion (NH + 4 ) are compounds. Remember that there is an ion dichromate. So dichromate would be part of an compound! 6

Writing IONIC Formulas (Criss-Cross Method) Write the formulas of the compounds produced from the listed ions. Cl - CO 3-2 OH - SO 4-2 PO 4-3 NO 3 - Na + NH 4 + Ca +2 Fe +3 Sn +4 1) Barium phosphate 2) Aluminum sulfide 3) Iron II bromide 4) Potassium nitride 5) Ammonium sulfide 6) Calcium oxide 7) Magnesium hydroxide 8) Chromium III oxide 9) Copper I sulfide 10) Tin IV oxide 7

Naming IONIC Compounds Name the following compounds: 1. CaCO 3 2. Pb(CH 3 COO) 2 3. FeSO 4 4. LiBr 5. MgCl 2 6. FeCl 3 7. Zn 3 (PO 4 ) 2 8. NH 4 NO 3 9. Al(OH) 3 10. PbSO 3 11. NaClO 3 12. Fe 2 O 3 13. (NH 4 ) 3 PO 4 14. NaHSO 4 15. CuCl 2 16. Mg(NO 2 ) 2 17. CuSO 4 18. NaHCO 3 19. NiBr 2 20. Ba(NO 3 ) 2 21. ZnSO 4 22. AuCl 23. KMnO 4 8

Naming MOLECULAR Compounds Name the following covalent compounds: 1. CO 2 2. CO 3. SO 2 4. SO 3 5. N 2 O 6. NO 7. N 2 O 3 8. NO 2 9. N 2 O 4 10. N 2 O 5 Write the formulas: Writing MOLECULAR Formulas 1. Phosphorous trichloride 2. Phosphorous pentachloride 3. Nitrogen trihydride 4. Sulfur hexachloride 5. Diphosphorous pentoxide 6. Carbon tetrachloride 7. Sulfur dioxide 8. Phosphorus tribromide 9

Naming Compounds Worksheet Hint: find molecular compounds FIRST and use prefixes!! 1. NH 4 I CaO 2 2. Fe 2 O 3 N 2 O 3 3. K 2 CO 3 Hg(NO 3 ) 2 4. FeI 2 Li 2 CO 3 5. PbNO 3 NaNO 3 6. NF 3 Ag 2 S 7. Mn(OH) 2 Hg 2 Cl 2 8. Mg 3 (PO 4 ) 2 KNO 3 9. Fe(CN) 2 N 2 S 3 10. Al 2 O 3 H 3 PO 4 11. Ca 3 (PO 4 ) 2 ZnCl 2 12. Al 2 (CO 3 ) 3 NH 4 F 13. K 2 O NaHCO 3 14. FeSO 4 NH 4 NO 3 15. CCl 4 PBr 3 10

Writing Formulas Worksheet Hint: find molecular compounds FIRST and use prefix rules!! 1. Barium permanganate Chromium II phosphite 2. Chromium II nitrate Mercury II sulfide 3. Sodium fluoride Copper II nitride 4. Lithium carbonate Tin II fluoride 5. Magnesium sulfate Tin IV bromide 6. Calcium nitrite Carbon tetrachloride 7. Barium bromide Phosphorus triodide 8. Chromium III acetate Dinitrogen hexafluoride 9. Carbon monoxide Chromium II hydroxide 10. Iron II sulfite Ammonium carbonate 11. Nickel II phosphate Barium hydroxide 12. Copper I chloride Barium chromate 13. Silver chromate Calcium sulfate 14. Zinc hydroxide Lead II carbonate 15. Mercury II nitrate Nickel II acetate 11

More PRACTICE W.F & N.C.!!! Name: Period: Naming Compounds: Writing Formulas: 1. CuCO 3 Oxygen difluoride 2. Cu(OH) 2 ammonium nitrate 3. Al 2 (SO 4 ) 3 silver nitrate 4. Fe(NO 3 ) 2 magnesium sulfite 5. (NH 4 ) 2 SO 4 lead II chromate 6. BaCl 2 sodium hydrogen sulfate 7. Na 2 CO 3 carbon dioxide 8. N 2 H 6 Phosphorus trichloride 9. MgSO 4 silver sulfide 10. P 2 O 5 aluminum hydroxide 11. NaHCO 3 Carbon disulfide 12. HgO iron III bromide 13. N 2 O 3 lead II sulfide 14. Na 2 O 2 potassium fluoride 15. HgCl 2 calcium peroxide 12

Review W.F & N.C. Worksheet Name: Period: Date: 1. What elements make up ionic compounds? 2. What elements make up molecular compounds? 3. Identify if the following compound is ionic (I) or molecular (M) and then write the formula or name the compound. a. N 2 O 5 b. FeCl 2 c. SF 6 d. NH 4 Cl e. PbCO 3 f. Carbon tetrachloride g. Magnesium hydroxide h. Dinitrogen tetroxide i. Ammonium phosphate j. Tin (IV) sulfate Naming Compounds: Writing Formulas: 1. SiCl 4 dinitrogen trifluoride 2. Pb 3 (PO 4 ) 2 ammonium oxide 3. Al(MnO 4 ) 3 lithium cyanide 4. Fe(NO 3 ) 2 disulfur decaflouride 5. (NH 4 ) 2 SO 4 chromium (III) chromate 6. B 2 H 6 Iron (III) sulfide 13

Unit Learning Map( 6 days): Writing Formulas & Naming Compounds Mrs. Hostetter Class: Academic Chemistry A - Grade 11 PA Standard: 3.4A : Explain the formation of compounds and their resulting properties using bonding theories (ionic and covalent). Recognize formulas for simple inorganic compounds. Unit Essential Question(s): Optional Instructional Tools: How do scientists represent compounds? Guided Notes Lab Materials: Bond w/ a classmate Ionic Lab Concept Concept Concept Concept Ionic Compounds Molecular Compounds Lesson Essential Questions: Lesson Essential Questions: Lesson Essential Questions: Lesson Essential Questions: How are ionic compounds named and written? How are molecular compounds named and written? Vocabulary: Vocabulary: Vocabulary: Vocabulary: Criss-Cross Method Ionic Formula Ionic compound Cation Anion Polyatomic ion Monatomic ion Molecular formula Molecular compounds 14

Writing Formulas & Naming Compounds Vocabulary: 1) criss-cross method = the positive and negative charges can be crossed over to give the subscripts. Ex: What is the formula of the compound formed by the ions of magnesium and bromine? o Ions = Mg +2 and Br -1 o Formula = Mg Br 2 2) Ionic compounds = compounds formed by an attraction between cations and anions Ionic compounds are usually a metal and a nonmetal 3) Ionic Formula = ions will combine in such a ratio that there will be a net charge of zero, forming a neutral compound. 4) Monatomic ion = ion formed from a single atom; Ex: S -2 and Fe +2 5) Polyatomic ion = a group of bonded atoms with a charge; Ex: NH 4 + and NO 3 6) Cation = positive ion b/c the parent atom lost electron(s) 7) Anion= negative ion b/c the parent atom gained electron(s) 8) Molecular formula = Chemical formula for a molecular compound 9) Molecular compounds = formula showing the types and numbers of atoms combined in a single molecule of a molecular compound Molecular compounds are usually 2 nonmetals 15

Guidelines for Writing Formulas & Naming Compounds: Guideline for WRITING IONIC FORMULAS: 1. Ionic compounds are usually created by joining a metal and a nonmetal 2. Write the symbol for the positive ion (cation) first, following by the negative ion (anion) 3. The subscript 1 is understood when NO subscript is present and is not written 4. Use parentheses around polyatomic ions when adding additional subscripts. a. PROTECT POLYATOMICS WITH PARENTHESES!! 5. Use the criss-cross method- the positive and negative charges can be crossed over to give the subscripts. Guideline FOR NAMING IONIC COMPOUNDS: d. Positively charged ion name comes first e. Negatively charged ion name comes second f. Ions with more than one charge/oxidation state, you have to figure out the charge and use the correct roman numerals! Guideline for WRITING MOLECULAR FORMULAS: 3. Prefixes tell you what the subscript will be! Ex: Carbon monoxide CO Ex: Carbon dioxide CO 2 Guideline for NAMING MOLECULAR COMPOUNDS: 1. A prefix is used with the name of the first element (one that is less electronegative) ONLY if more than one atom of that element is present. Ex: NO is called nitrogen monoxide Ex: N 2 0 is called dinitrogen monoxide 2. The second element is named by combining (a) a prefix if more than one compound can be formed by the two elements (b) the root of the name of the second element, and (c) the ending ide 3. Hints to use when molecular and ionic compounds are on the same worksheet/test: Determine if the compound is molecular or ionic. Molecular compounds ONLY contain NONMETALS. Ionic compounds ONLY contain METALS and NONMETALS. Compounds that contain ammonium ion (NH 4 + ) are IONIC compounds. Remember that there is an ion dichromate. So dichromate would be part of an IONIC compound! 16