1. Modern Chemistry Chapter 7 Chemical Formulas and Chemical Compounds

2. Chemical Names and Formulas
Section 1
Chemical Names and Formulas

3. Chemical Formula C H Molecular compounds – for one molecule
Ionic compounds – for one formula unit; the simplest ratio of cations to anions C H 8 18
Eighteen hydrogen atoms in the molecule
Eight carbon atoms in the molecule

4. Chemical Formula Al (SO )
5 ions – two Al 3+ ions and three (SO4) 2- ions Al
(SO ) 2 4 3
4 SO4 ions
2 Al atoms
4 O atoms

5. Definitions Binary Compound – compound with only two types of atoms
Nomenclature – a naming system
Salt- an ionic compound composed of a cation and an anion from an acid

6. Definitions Monatomic ions – ions formed from a single atom
For negative monatomic ions, -ide is added to the root name

7. How can I tell if the compound is ionic or covalent ????
Ionic compounds contain a metal and a nonmetal or a polyatomic ion !!!

8. Writing Fomulas and Naming
Ionic Compounds

9. Charges on Monatomic Ions1+ 2+ 3+ 3- 2- 1-

10. Charges on Transition Metals
Ag 1+
Zn 2+
Cu 1+ or 2+
Fe/Cr 2+ or 3+
Sn 2+ or 4+
Pb 2+ or 4+
See list.

11. Charges of Metals
PbO2 and PbO

12. Polyatomic Ions Page 226

13. Ionic Compounds Formulas Write the symbols Determine the charges
Monatomic ions from the periodic table
Transition metals from a roman numeral
Polyatomic ions from sheet.
Cross the charges.
Reduce to lowest ratio.

14. Ionic Compounds Names Write the cation name. Write the anion name.
Add –ide to the anion if monatomic
Add the roman numeral for any transition metal.
NO PREFIXES!!!!

15. Ionic Binary Compounds
Aluminum Oxide
FORMULAS 3+ 2- Al O 3 2
(3+ x ) + (2- x ) = 0 2 3
Al2O3
(charge x subscript)+(charge x subscript) = 0

16. Ionic Binary Compounds
Aluminum Oxide
FORMULAS 3+ 2- Al O 3 2
REDUCE IF NECESSARY!!
Al2O3

17. Ionic BinaryCompounds
NAMING
Mg3N2
NO PREFIXES!!
Magnesium
Nitrogen
ide

18. 1. Write formulas for the binary ionic compounds formed between the following elements:
a. potassium and iodine
b. magnesium and chlorine
c. sodium and sulfur
d. aluminum and sulfur
e. aluminum and nitrogen
2. Name the binary ionic compounds indicated by the following formulas:
a. AgCl e. BaO
b. ZnO f. CaCl2
c. CaBr2
d. SrF2
Practice Page 223

19. Ionic Compounds with Transition Metals
FORMULAS
Iron (III) Chloride 3+ 1- Fe Cl 1 3
(3+ x ) + (1- x ) = 0 1 3
FeCl3

20. Ionic Compounds with Transition Metals
FORMULAS
Tin (II) Oxide 2+ 2- Sn O 1 1
(2+ x ) + (2- x ) = 0 1 1
SnO

21. Ionic Compounds with Transition Metals
FORMULAS
Tin (II) Oxide 2+ 2- Sn O 2 1 1 2
REDUCE!
SnO

22. 1. Write the formula and give the name for the compounds formed between the following ions:
a. Cu 2+ and Br − d. Hg 2+ and S 2−
b. Fe 2+ and O 2− e. Sn 2+ and F −
c. Pb 2+ and Cl − f. Fe 3+ and O 2−
2. Give the names for the following compounds:
a. CuO c. SnI4
b. CoF d. FeS
Practice Page 225

23. Ionic Compounds with Transition Metals
NAMING
PbO
( x 1 ) ( 2- x 1 ) = 0 2+
NO PREFIXES!!
Lead II
Oxygen
ide

24. Ionic Compounds with Polyatomic Ions
FORMULAS
Ammonium Sulfate + 2-
(NH )
(SO ) 4 2 4 1
(1+ x ) (2- x ) = 0 2 1
(NH4)2SO4
Parenthesis are needed if the p. ion has a subscript from the crossed charge – outside the ( ).

25. Ionic Compounds with Polyatomic Ions
NAMING
Ca(NO3)2
NO PREFIXES!!
Calcium
Nitrate

26. Practice Page 227 1. Write formulas for the following ionic compounds:
a. sodium iodide e. copper(II) sulfate
b. calcium chloride f. sodium carbonate
c. potassium sulfide g. calcium nitrite
d. lithium nitrate h. potassium perchlorate
2. Give the names for the following compounds:
a. Ag2O
b. Ca(OH)2
c. KClO3
d.NH4OH
e. Fe2(CrO4)3
f. KClO
Practice Page 227

27. Writing Fomulas and Naming
Molecular Compounds

28. Prefixes for Covalent
p. 228

29. Molecular Compound Formulas Write the symbols.
Use prefixes for subscripts.
DON’T reduce.

30. Molecular Compound Names Write the name of the elements.
Order: Smaller group number first;
Same group? Greater period number first.
Add –ide to the second element.
Add prefixes to each element for the number of atoms.

31. Binary Molecular Compounds
FORMULAS
Disulfur difluoride S F 2 2
DON'T REDUCE!
S2F2

32. Binary Molecular Compounds
NAMING O N 2 4 di
nitrogen
tetra
oxygen
ide

33. Practice Page 229 1. Name the following binary molecular compounds:
a. SO3
b. ICl3
c. PBr5
2. Write formulas for the following compounds:
a. carbon tetraiodide
b. phosphorus trichloride
c. dinitrogen trioxide
Practice Page 229

34. Acids and Salts Acids – Chapter 14
Binary Acids – two elements; hydrogen and one other element
Oxyacids – contain hydrogen, one other element and oxygen
Acid – typically thought of as an H donor; usually referred to as a solution of the compound in water.

35. Acids and Salts Salt – an ionic compound Made from
the cation of a base and
the anion of an acid
Some retain an H in the anion
Example: CO3 2- carbonate
HCO3 1- hydrogen carbonate or bicarbonate

36. Salt Definition Animation
p. 230

37. HF, HCl, H3PO4, HNO3, H2SO4 CH3COOH
List of Acids
Know these acids:
HF, HCl, H3PO4, HNO3, H2SO4 CH3COOH
p. 230

38. Section 3
Oxidation
Numbers

39. Oxidation Numbers
Oxidation numbers are numbers assigned to the atoms in a molecular compound or ion that indicates the general distribution of electrons among bonded atoms.
Oxidation numbers are not actual charges.
Oxidation numbers can be useful in naming compounds and writing formulas. -1 +1 +2 +3 -2

40. Rules for Assigning Oxidation Numbers
Atoms in a pure element have an oxidation number of zero – O2 Ox. # = 0
Fluorine always has ox. # of -1
Oxygen almost always has ox. # of -2 except in peroxides such as H2O2 – then it is a -1.

41. Rules for Assigning Oxidation Numbers
(Rules continued):
Hydrogen’s ox. # is +1 unless it is with metals – then it is -1
The sum of the ox. # in molecules must be zero, but in polyatomic ions, it is equal to the ions charge.

42. Oxidation Numbers
What are the oxidation numbers for each atom in these compounds?
UF6 : Fluorine is -1 x 6 = -6
Uranium +6 {+6 + (-6)} = 0
H2SO4 : Oxygen is -2 (x 4 = -8)
Hydrogen is +1 (x 2 = +2) so
Sulfur has to be +6
{ (+6) + (+2) + (-8) }= 0

43. Oxidation Numbers
What are the oxidation numbers for the chlorate polyatomic ion?
ClO3- : Oxygen is -2 x 3 = -6
Chlorine must be +5
{ (+5) + (-6)} = -1 (the ion’s charge)

44. Using Chemical Formulas
Section 4
Using Chemical Formulas

45. Formula Mass
With a chemical formula, you can calculate many characteristic values for a compound.
Formula Mass:
Compounds have masses – just like elements.

46. Formula Mass Formula Mass:
The formula mass of any molecule, formula unit, or ion is the sum of the average atomic masses of all the atoms represented in its formula.
To find the mass of a compound simply add the masses of the atoms that make up the compound. Units are amu’s.

47. Formula Mass To find the formula mass of sulfuric acid (H2SO4):
element # of atoms x mass (to 2 decimals)
H = amu
S =32.01 amu
O =64.00 amu
98.03 amu

48. Formula Mass To find the formula mass of Calcium Nitrate Ca(NO3)2
element # of atoms x mass =
Ca =40.08 amu
N =28.02 amu
O = amu
amu

49. Molar Mass
Molar Mass
The mass of a mole of any substance is equal to its formula mass – except instead of amu’s it is in grams.
Formula mass of sulfuric acid = amu
Molar mass of sulfuric acid = grams

50. Molar Mass To find the molar mass of Calcium Nitrate Ca(NO3)2
element # of atoms x mass =
Ca =40.08 g
N =28.02 g
O = g g

51. Percentage Composition
It is sometimes useful to know what the percentage of a compound is an element.
What percentage of water is oxygen?
H: x 2 = 2.02
O: x 1 = 16.0
Molar Mass= g
16.0 ÷18.02 = 88.79%

52. Molar Mass Molar Mass can be used as a conversion factor. 1 mole H2SO4
98.03 grams or
98.03 grams
1 mole H2SO4

53. Problems How many moles are there in 25 g of H2SO4? 1 mole H2SO4
25 g H2SO4 x =
0.255 mol
98.03 grams

54. Problems What is the mass of 4.2 moles of H2SO4? x = 1 mol H2SO4
98.03 g H2SO4
4.2 mol H2SO4 x =
mol
1 mol H2SO4

55. Problems How many molecules are in 54 g of H2SO4?
6.02 x 1023 molecules H2SO4
54 g H2SO4 = x
98.03 g H2SO4
3.32 x 1023 molecules

56. Determining Chemical Formulas
Section 4
Determining Chemical Formulas

57. Chemical Formula from % Comp
Check periodic table for molar masses of each element
Find moles of each element present (assume 100g since we are working with percentages)
To determine the simplest ratio of moles in the compound, select the smallest number of moles calculated and divide the other moles calculated by that number
Write the formula using the smallest whole number ratio of elements

58. Empirical formulas Simplest formula
Consists of element symbols and subscripts showing the numbers of each element
Really, subscripts represent the smallest whole number ratios

59. Empirical formulas
What is the empirical formula of a compound containing 56.6% K, 8.7% C and 34.7 % O ?
K= g/mol
C = g/mol
O = g/mol

60. Empirical formulas K 56.6 g K x 1 mol K = 1.45 mol 39.10 g K
C 8.7 g C x 1 mol C = mol
12.01 g C
O g O x 1 mol O = 2.17 mol
16.00 g O
Smallest value = Divide all answers by this number.

61. Empirical formulas K = 1.45 mol = 2.00 0.724 mol C = 0.724 mol = 1.00
O = 2.17 mol = 3.00
Therefore, the empirical formula = K2CO3
Name?
Potassium Carbonate

62. Molecular formulas
Gives the type and actual number of atoms in the compound
CH2O – empirical formula for glucose
C6H12O6 – molecular formula for glucose
So far, we have been studying ionic compounds, so molecular and empirical formulas were the same
In most compounds, however, not the same

63. Molecular formulas
Molecular formulas can be determined from empirical formulas
X (empirical formula) = molecular formula
(X is a whole number)
Also true . . .
Molecular molar mass = X
Empirical molar mass

64. Molecular formulas
Empirical formula of mercury (I) chloride is HgCl. What is the molecular formula, knowing that molar mass is g/mol?
Empirical formula HgCl
Molar mass of unknown = g/mol
1 mol Hg = g/mol
1 mol Cl = g/mol
Molar mass of HgCl = g/mol

65. Molecular formulas 472.08 g/mol = 2.00 236.04 g/mol 2(HgCl) = Hg2Cl2
Name?
dimercury dichloride