Chemical formula - combination of symbols that represent the composition of a compound

1. Chemical formula - combination of symbols that represent the composition of a compound • Shows elements present and number of atoms

2. subscripts • Represent the number of atoms of that element in the compound • No subscript is an “understood” 1

3. NaCl • 1 Na 1 Cl • H2SO4 • 2 H 1 S 4 O • Ca(ClO3)2 ????? • 1 Ca 2 Cl 6 O

4. Two types of compounds we will learn how to write formulas for Ionic – transfer of electrons Covalent – share electrons (called Molecular)

5. Molecular Compounds (covalent) • Representative unit – “molecule” (bonded covalently) • Type of elements – nonmetals • Physical state – solid, liquid, gas • Solids – low melting point, brittle

6. Molecule – electrically neutral group of atoms that act as a unit

7. Naming binary molecular compounds • 2 elements in the compound • Both nonmetals! • 2 naming systems • Prefix system • Stock system (roman numerals) • Both systems are correct • I’m sure you will prefer the prefix system!

8. Prefixes you must memorize! Number of Prefix used atoms 1 mono 2 di 3 tri 4 tetra 5 penta 6 hexa 7 hepta 8 octa 9 nona 10 deca

9. When 2 nonmetallic elements combine • Often do so in more than one way • Example CO CO2 • Problem with calling them both “carbon oxide”

10. CO2 – you exhale. It is normally present in the air you breathe • CO – hopefully is not in the air you breathe • In large amount R.I.P. • Catalytic converter – cars • Converts CO to CO2

11. Naming binary molecular compounds • Prefix + first element name • Followed by prefix + 2nd element name with “ide” ending • ******only time you can not use a prefix is if the first element in the compound is a single atom

12. PCl3 phosphorus trichloride • CO • Carbon monoxide (not monocarbon monoxide!)

13. Don’t use “double vowels” • Change if a “tongue twister” • Monooxide  monoxide • Decaoxide  decoxide • Trioxide – is fine

14. N2O • Dinitrogen monoxide • SF6 • Sulfur hexafluoride • N2H4 • Dinitrogen tetrahydride • NO FACTORING ALLOWED!!!

15. P2O3 • Diphosphorus trioxide

16. Name the following: • CS2 • Carbon disulfide • Cl2O7 • Dichlorine heptoxide • P4O10 • Tetraphosphorus decoxide

17. N2O5 • Dinitrogenpentoxide • CCl4 • Carbon tetrachloride

18. Write formulas for the following: • carbon tetrabromide • CBr4 • dinitrogen tetrahydride • N2H4

19. boron trichloride • BCl3 • diphosphorus trioxide • P2O3

20. A molecular compounds worksheet just for you!!

25. IONIC COMPOUNDS • Four different types we will learn about

26. Metal + nonmetal (binary ionic) • Metal + polyatomic ion • Polyatomic ion + polyatomic ion • Polyatomic ion + nonmetal

27. Ionic Charges • Monatomic ions – ions consisting of only one atom • Charges can often be determined by using the periodic table • Metallic elements – tend to lose electrons to form cations • Group 1 – all 1+ • Group 2 – all 2+

28. Nonmetals • Nonmetals tend to gain electrons when they bond with metals – form anions

29. Transition metals • Many have more than one common ionic charge Are going to use roman numerals I, II, III, IV, V

31. Oxidation number • Indication of how many electrons it will gain or lose when it forms a bond • Gains or loses electrons – forms an ion • Charged particle • Can be found for each element on the periodic table • Refer to yours!!!

32. Some elements have more than 1 oxidation number – that means they can form more than one type of compound

33. When a single atom takes on a charge (by gaining or losing electrons) – it forms a “monatomic ion” • Ion made up of more than 1 atom – “polyatomic” ion

34. Monatomic ions • Na+ Ca+2 Cl- O-2 • Polyatomic ions • CO3-2 ClO3- OH-

35. Why would an atom want to form an ion? • Remember the “octet rule” • Wants a filled outer shell • For most atoms, that is 8

36. Samples on board using electron dot notation • Na and Cl • Ca and Cl • Al and Cl • Ca and S • K and N you do

37. 1) Metal + nonmetal • Metal always written first – has positive oxidation number (written first) • Nonmetal written second – has negative oxidation number

38. Can use “criss-cross” method to arrive at correct formula. • Must remember to factor subscripts if possible!! • Magnesium oxide - MgO

39. Naming binary ionic compounds • Metal full name first • Nonmetal name with “ide” ending • NaCl sodium chloride • CaCl2 calcium chloride • LiF lithium fluoride • AlBr3 aluminum bromide

40. Some metals have multiple oxidation numbers • Use Roman numerals to specify the oxidation number used • I, II, III, IV, V, VI, VII, VIII • Transition metals characteristically have multiple oxidation numbers • ONLY USE ROMAN NUMERALS IF THE METAL HAS MORE THAN ONE OXIDATION NUMBER LISTED

41. Nonmetals may have more than one oxidation number, you just use the first number listed - NEGATIVE

42. Examples: • Co, Ni, Cu, Fe, Mn • Always check before writing name for the compound • FeCl2 • Iron(II) chloride • FeO • Fe2O3

43. Write formulas for the following • calcium sulfide • CaS • strontium bromide • SrBr2 • chromium(III) chloride • CrCl3

44. iron(II) oxide • FeO

45. Name the following compounds • Fe2O3 • Iron(III) oxide • KI • Potassium iodide • CuO • Copper(II) oxide

46. NiCl3 • Nickel(III) chloride • CrO3 • Chromium(VI) oxide

47. 2. Metal + polyatomic ion • Almost all polyatomic ions have a negative charge • 2 you are responsible for have a positive charge NH4+ and H3O+ • Polyatomic ions travel as a unit • Page 102 in text - list of polyatomic ions • You will use the table I gave you

48. NEVER CHANGE THE SUBSCRIPTS IN A POLYATOMIC ION • THAT MEANS NEVER!!!!!!!

49. Can use same “criss-cross” method for determining the correct formula • Same rules apply – must factor the subscripts if you can (only the oxidation numbers that are used – NOT THE SUBSCRIPTS OF THE POLYATOMIC ION!!!!!!

50. At first, always put a parenthesis around the polyatomic ion • Only time the parenthesis can be dropped is if a “1” criss-crosses down or if the subscript factors to a “1”