Key Question: Why Do Atoms Combine In Certain Ratios?

1. Key Question: Why Do Atoms Combine In Certain Ratios?

2. Review of Oxidation Numbers

3. Review of Oxidation Numbers All compounds have an electrical charge of zero (they are neutral). An oxidation number indicates the charge on the atom (or ion) when electrons are lost, gained, or shared in chemical bonds.

4. Oxidation Numbers A sodium atom always ionizes to become Na+ (a charge of +1) when it combines with other atoms to make a compound. Therefore, we say that sodium has an oxidation number of 1+. What is chlorine’s oxidation number?

6. Ionic Bonds On the periodic table, strong electrondonorsare on the left side (alkali metals). Strong electron acceptors are on the right side (halogens). The further apart two elements are on the periodic table, the more likely they are to form an ionic compound.

8. Covalent Bonds Covalent compounds form when elements have roughly equal tendencies to accept electrons. Elements that are both nonmetals and therefore close together on the periodic table tend to form covalent compounds.

9. Oxidation Numbers, Lewis Structures And Chemical Formulas Remember, the oxidation numbers for all the atoms in a compound must add up to zero.

11. Multiple Oxidation Numbers Some periodic tables list multiple oxidation numbers for most elements. This is because more complex bonding is possible.

12. Naming Compounds and Writing Formulas

13. 5 Types Of Chemical Compounds • Binary ionic - metal ion – nonmetal ion • Ternary ionic - at least one ion is a polyatomic ion • Binary molecular - two nonmetals • Binary acid - H – nonmetal • Ternary acid - H – Polyatomic ion

14. Tips To Keep In Mind When Naming And Writing Formulas: • Always keep your Periodic Table handy – You should have it in front of you ALWAYS when you are naming and writing formulas. • Remember that metals (except Hydrogen) are found to the left of the stairstep on the Periodic Table. • Nonmetals are found on the right side of the stairstep of the Periodic Table. • Metalloids are the 7 elements on or below the stairstep except Al and At. For naming purposes they will tend to behave like nonmetals.

16. Naming Binary Compounds A binary ionic compoundis held together by ionic bonds. Binary molecular compoundsconsist of covalently bonded atoms. Each type of compound has its own naming rules.

17. How Do You Name Binary Ionic Compounds? • (Composed Of Two Elements – A Metal And A Nonmetal) • Name the first ion • From groups 1, 2, 3, 13, zinc, cadmium, or silver. (You must use a Roman Numeral with the name for the other metals – we’ll discuss this later.) • Name the second ion changing the suffix to –ide.

18. Naming Binary Ionic Compounds MgBr2 is magnesium(name of first element) + brom(root name of second element) + idesuffix = magnesium bromide

19. Examples This is two metals – not a binary ionic compound BaNa2 You should recognize a problem with this one The name of this is Banana (haha!!) What is the name of this compound: HIJKLMNO? WATER – “H” to “O” You have to admit – that was funny!

20. Exit Quiz NaCl Sodium Chloride Name the metal ion CaO Name the nonmetal ion, changing the suffix to –ide. Oxide Calcium Al2S3 Aluminum Sulfide MgI2 Magnesium Iodide

21. 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. Iron (II) Oxide How do you know the charge? Deductive reasoning. • All compounds are neutral. • Oxygen has a -2 charge (group 16) • Therefore, iron must have a +2 charge since there is one iron and one oxygen. Iron gets a Roman Numeral (II). Isn’t this easy and FUN!!!

22. 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 16) • There are two coppers. • Therefore each copper must have a +1 charge for all ions to be neutral Cu2S Copper (I) Sulfide

23. 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

24. So Why Must We Use Roman Numerals With Transition Elements? • The metals in groups 1, 2, 3, and 13 have single, definite charges. • Group 1 metals have a +1 charge. • Group 2 metals have a +2 charge. • Groups 3 and 13 metals have a +3 charge. • Transition metals may have multiple charges – usually two different positive charges. • For example, there are two copper oxide compounds: CuO Copper II oxide Copper is +2 Cu2O and CuO Cu2O Copper I oxide Copper is +1 We can’t just say Copper oxide. Which one of these is Copper oxide? We must distinguish these by using a Roman Numeral

25. There Are Three Transition Elements Which Do Not Require A Roman Numeral Because They Have Single Definite Charges. These Are Zinc – Zn2+ Cadmium – Cd2+ Silver – Ag+ You need to remember the charges for these. Ag2O Name the first ion. Name the second ion changing the suffix to –ide. oxide Silver No Roman Numerals needed for these. ZnCl2 Name the first ion. Zinc chloride Name the second ion changing the suffix to –ide.

26. How Do You Write Formulas For Binary Ionic Compounds Given The Name? • Two Simple Steps: • Write the symbol and charge of each ion • Balance the charges by providing subscripts Magnesium chloride Write the symbol and charge of each ion. Mg2+ Cl- Balance the charges by supplying subscripts. Subscripts tell how many of each atom is present. Cl- MgCl2 You need a second Cl-1 to balance the charges

27. Iron (III) bromide Fe3+ Br - Write the symbol and charge of each ion. The charge of the iron is provided by the Roman Numeral. Br - Br - FeBr3 Balance the charges by supplying subscripts. The subscripts tell how many of each ion is needed to balance the compound. You’ll need three bromine ions to balance the one iron.

28. Aluminum Sulfide Write the symbol and charge of each ion. Al3+ S2- Balance the charges by supplying subscripts. Al3+ S2- In this case the charges do not evenly divide into each other. You must find the least common multiple. SIX S2- Al2S3 How many aluminums are needed to arrive at a +6 charge? 2 How many sulfurs are needed to arrive at a -6 charge? 3

29. Writing Formulas a Little Quicker Iron and oxygen combine to form a compound. Iron (Fe) has an oxidation number of 3+. Oxygen (O) has an oxidation number of 2–. Predict the chemical formula of this compound.

30. Given … Fe3+ and O2– Write the subscripts so that the sum of the oxidation numbers equals zero. Solution Two iron atoms = 2 × (3+) = 6+ Three oxygen atoms = 3 × (2–) = 6– Writing Formulas a Little Quicker

31. Writing Formulas a Little Quicker 2- 3+ Fe O 3 x 2 = 6

32. 2- 2- 2- 3+ 3+ Fe Fe O O O = -6 = +6 0 Writing Formulas a Little Quicker + + + +6 -6

33. Writing Formulas a Little Quicker 2- 3+ Fe O 2 3

34. Exit Quiz – Formula for magnesium chloride? 2+ 1- MgCl2

35. Exit Quiz – Formula for sodium oxide? 1+ 2- Na2O

36. Exit Quiz – Name for: 3+ 2- Fe2O3 Iron (III) oxide

37. Exit Quiz – Formula for: 4+ 2- CrO2 Chromium (IV) oxide

38. Exit Quiz – Charge on Chromium? 6+ 2- Cr2O72-

39. Second Category Of Compounds – Ternary Ionic 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.

40. CO32- carbonate This ion is composed of one carbon and three oxygens and the entire group has a charge of -2. Polyatomic ion – Group of atoms that act as a unit and carry a charge. You have been given a list of other polyatomic ions You need to learn these!!!

41. How Do You Recognize Ternary Ionic Compounds? • Composed of two ions in which at least one is a polyatomic ion. • There is only one positive polyatomic ion (NH4+) • Three possible types of Ternary Ionic Compounds: • Ammonium + negative ion (nonmetal) • Metal (positive ion) + negative polyatomic ion • Ammonium + negative polyatomic ion Polyatomic Ion

42. Naming Compounds with Polyatomic ions NH4Cl is ammonium(the name of the ion from chart) + chlor(root name of the second element) + idesuffix= ammonium chloride.

43. How Do You Name Ternary Ionic Compounds? • Name the first ion. • Name the second ion. Isn’t that simple??!! • Examples: 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 Sodium carbonate Notice that you do NOT change the suffix – just name the polyatomic ion Name the first ion. Name the second ion.

44. Fe(OH)3 Name the first ion. Remember that iron requires a Roman Numeral since it is a transition element. What Roman Numeral should be used? Iron (III) hydroxide 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) Name the polyatomic ion.

45. NH4Cl Name the first ion. Ammonium Name the second ion. chloride Notice that since the second ion is a nonmetal that, like binary ionic compounds, the suffix of the nonmetal changes to –ide. Name the first ion. (NH4)3PO4 Ammonium phosphate Name the second ion. Looks like a monster, but it’s really a pussycat.

46. Cu2SO4 Name the first ion. You should realize that you need a Roman Numeral since copper is a transition metal. sulfate Copper (I) The Roman Numeral is the same as the charge. What is the charge? The charge of sulfate is -2. Since there are two coppers, the charge of the copper must be +1. Name the second ion.

47. 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 supplying subscripts. • If a subscript is needed for a polyatomic ion, it must be put in parentheses with the subscript on the outside. • Let’s do some!!

48. Aluminum nitrate First, you can tell from the name that there is a polyatomic ion present (nitrate). All binary ionic compounds have suffixes of –ide. Al3+ NO3- Al(NO3)3 Write the formula/symbol and charge of each ion. Balance the charges by supplying subscripts. Since Al is +3 and NO3 is -1, you need a total of 3NO3- to balance one Al3+ Since you will need a subscript of 3 for NO3-, you need to put this in parentheses with the 3 outside.

49. Lead (IV) acetate Write the formula/symbol and charge of each ion. Pb4+ C2H3O2- Balance the charges by supplying 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 Ca2+ PO43- Balance the charges by supplying subscripts. Since Ca is +2 and PO4 is -3, you will need 3 Ca+2 to balance 2 PO4-3 Ca3(PO4)2

50. Exit Quiz Al3+ combines with sulfate (SO4)2– to make aluminum sulfate. Write the chemical formula for aluminum sulfate.