1. Chemical Formulas and Chemical Compounds Chapter 7

2. Systematic Naming There are too many compounds to remember the names of them all. Compound is made of two or more elements. Name should tell us how many and what type of atoms.

3. Significance of a Chemical Formula Molecular formulas Number of atoms of each element in one molecule of a compound C 2 H 6 = ethane (2 carbon atoms, 6 hydrogen atoms) Ionic Compounds Represents the simplest whole number ratio of the compounds cations and anions Al 2 (SO 4 ) 3 = aluminum sulfate (2 aluminum ions, 3 sulfate ions)

4. Charges on ions For most of Group A elements, location on the Periodic Table can tell what kind of ion they form Elements in the same group have similar properties. Including the charge when they are ions.

5. 2+ 1+ 3+3-2-1- Charge in groups 1A, 2A and 3A is the group number

6. Naming Monatomic Ions 1. Monatomic cations Identified by the element’s name 2. Monatomic anions Drop the ending of the element name Add an “–ide” ending

7. Name these l Na 1+ Sodium ion l Ca 2+ Calcium ion l Al 3+ Aluminum ion l Li 1+ Lithium ion

8. Write Formulas for these l Potassium ion K 1+ l Magnesium ion Mg 2+ l Copper(II) ion Cu 2+ l Chromium(VI) ion Cr 6+ l Barium ion Ba 2+ l Mercury(II) ion Hg 2+

9. Name these l Cl 1- Chloride ion l N 3- Nitride ion l Br 1- Bromide ion l O 2- Oxide ion l Ga 3+ Gallium ion

10. Write these l Sulfide ionS 2- l Iodide ionI 1- l Phosphide ionP 3- l Strontium ionSr 2+

11. Day 2

12. Binary Ionic Compounds Binary Compounds Compounds composed of two different elements Binary ionic cmpd, total # of positive and negative charges must equal

13. Writing Formulas for Binary Ionic Compounds Write the symbols for the ions side by side. ALWAYS write the cation first! Al 3+ O 2- Cross over the charges by using the absolute value of each ion’s charge as the subscript for the other ion Al 2 3+ O 3 2- Check that the subscripts are in smallest whole number ratio Al 2 O 3

14. Naming Binary Ionic Compounds Al 2 O 3 1. Name the cation(don’t change) Aluminum 2. Name the anion (drop add-ide) Oxide Aluminum Oxide

15. Click below to watch the Visual Concept. Visual Concept Section 1 Chemical Names and Formulas Naming Ionic Compounds

16. The Stock System of Nomenclature Most transition metals can have more than one type of charge. Indicate the charge with Roman numerals in parenthesis. Fe 2+ Iron(II) Fe 3+ Iron(III) Roman numerals are never used: For anions For metals that form only one ion Co 2+ Cobalt(II) ion CuCl 2 Copper(II) chloride

17. Naming ions Cont….. A few, like silver, zinc and cadmium only form one kind of ion Don’t get roman numerals Ag + silver ion Zn 2+ zinc ion Cd 2+ cadmium ion

18. Compounds Containing Polyatomic Ions Naming a series of similar polyatomic ions NO 2 - NO 3 - Nitrite Nitrate Most common ion is given –ate ending, ion with one less oxygen –ite Pg 214 Naming compounds containing polyatomic ions Same as for monatomic ions

19. Day 3

20. Molecular Nomenclature Prefix System (binary compounds) 1.Less e - neg atom comes first. 2.Add prefixes to indicate # of atoms. Omit mono- prefix on first element. 3.Change the ending of the second element to -ide.

21. PREFIX mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca- NUMBER 1 2 3 4 5 6 7 8 9 10 C. Molecular Nomenclature

22. Click below to watch the Visual Concept. Visual Concept Section 1 Chemical Names and Formulas Naming Covalently-Bonded Compounds

23. Click below to watch the Visual Concept. Visual Concept Section 1 Chemical Names and Formulas Naming Compounds Using Numerical Prefixes

24. CCl 4 N 2 O SF 6 carbon tetrachloride dinitrogen monoxide sulfur hexafluoride Molecular Nomenclature

25. arsenic trichloride dinitrogen pentoxide tetraphosphorus decoxide AsCl 3 N2O5N2O5 P 4 O 10 Molecular Nomenclature

26. Day 4

27. Oxidation Numbers also known as the oxidation state is a simple record-keeping concept, to help in remembering of formulas and chemical phenomena also allow for easy classification and naming of new compounds Rules see pg 220

28. Click below to watch the Visual Concept. Visual Concept Section 2 Oxidation Numbers Rules for Assigning Oxidation Numbers

29. Day 5

30. Percent Composition the percentage by mass of each element in a compound

31. Click below to watch the Visual Concept. Visual Concept Section 3 Using Chemical Formulas Percentage Composition

32. Find the % composition of Cu 2 S.  100 = %Cu = 127.10 g Cu 159.17 g Cu 2 S  100 = %S = 32.07 g S 159.17 g Cu 2 S 79.852% Cu 20.15% S

33. %Fe = 28 g 36 g  100 = 78% Fe %O = 8.0 g 36 g  100 = 22% O Percent Composition Find the percentage composition of a sample that is 28 g Fe and 8.0 g O.

34. Percentage Composition How many grams of copper are in a 38.0-gram sample of Cu 2 S? (38.0 g Cu 2 S)(0.79852) = 30.3 g Cu Cu 2 S is 79.852% Cu

35.  100 = %H 2 O = 36.04 g 147.02 g 24.51% H 2 O Percent Composition Find the mass percentage of water in calcium chloride dihydrate, CaCl 2 2H 2 O?

36. Using Chemical Formulas Formulas mass-sum of all the average atomic masses of all the atoms in the formula H 2 O =18.02 amu A compound’s formula mass is equal to compounds molar mass H 2 O = 2 Moles of Hydrogen 1 mole of Oxygen 18.02 g/mol

37. Empirical Formula Smallest whole number ratio of atoms in a compound C2H6C2H6 CH 3 reduce subscripts

38. Empirical Formula 1. Find mass (or %) of each element. 2. Find moles of each element. 3. Divide moles by the smallest # to find subscripts. 4. When necessary, multiply subscripts by 2, 3, or 4 to get whole #’s.

39. Empirical Formula Find the empirical formula for a sample of 25.9% N and 74.1% O. 25.9 g 1 mol 14.01 g = 1.85 mol N 74.1 g 1 mol 16.00 g = 4.63 mol O 1.85 mol = 1 N = 2.5 O

40. Empirical Formula N 1 O 2.5 Need to make the subscripts whole numbers  multiply by 2 N2O5N2O5

41. Molecular Formula “True Formula” - the actual number of atoms in a compound CH 3 C2H6C2H6 empirical formula molecular formula ?

42. Molecular Formula 1. Find the empirical formula. 2. Find the empirical formula mass. 3. Divide the molecular mass by the empirical mass. 4. Multiply each subscript by the answer from step 3.

43. Molecular Formula The empirical formula for ethylene is CH 2. Find the molecular formula if the molecular mass is 28.1 g/mol? 28.1 g/mol 14.03 g/mol = 2.00 empirical mass = 14.03 g/mol (CH 2 ) 2  C 2 H 4

44. Click below to watch the Visual Concept. Visual Concept Section 4 Determining Chemical Formulas Comparing Molecular and Empirical Formulas