1. Preview Lesson Starter Objectives Significance of a Chemical Formula
Monatomic Ions
Binary Ionic Compounds
Writing the Formula of an Ionic Compound
Naming Binary Ionic Compounds
Naming Binary Molecular Compounds
Covalent-Network Compounds
Acids and Salts

2. Lesson Starter Chapter 7 CCl4 MgCl2
Section 1 Chemical Names and Formulas
Chapter 7
Lesson Starter
CCl MgCl2
Guess the name of each of the above compounds based on the formulas written.
What kind of information can you discern from the formulas?
Guess which of the compounds represented is molecular and which is ionic.
Chemical formulas form the basis of the language of chemistry and reveal much information about the substances they represent.

3. Objectives Chapter 7 Explain the significance of a chemical formula.
Section 1 Chemical Names and Formulas
Chapter 7
Objectives
Explain the significance of a chemical formula.
Determine the formula of an ionic compound formed between two given ions.
Name an ionic compound given its formula.
Using prefixes, name a binary molecular compound from its formula.
Write the formula of a binary molecular compound given its name.

4. Significance of a Chemical Formula
Chapter 7
Section 7.1 Chemical Names and Formulas
Significance of a Chemical Formula
A chemical formula shows the number of atoms of each kind in a chemical compound.
For a molecular compound it shows the number of atoms of each element contained in a single molecule.
example: octane — C8H18
1 molecule = 8 C atoms, 18 hydrogen atoms

5. Significance of a Chemical Formula, continued
Section 7.1 Chemical Names and Formulas Formulas
Significance of a Chemical Formula, continued
The chemical formula for an ionic compound represents one formula unit
One formula unit is the simplest ratio of the compound’s positive ions (cations) and its negative ions (anions).
example: aluminum sulfate — Al2(SO4)3
2 Al ions to 3 sulfate ions or
2 Al atoms, 3 sulfur atoms, 12 oxygen atoms

6. Understanding Chemical Formulas
Subscript: Tells how many atoms of each element are in the chemical formula (one is never written)
Subscripts are multiplied by what is in parentheses ( ).
A chemical formula represents one formula mass of the compound in amu.

7. Formula Mass
Formula mass is the sum of all the individual atomic masses of the elements in a chemical formula expressed in amu’s.
The formulas mass = molar mass (g)
Molar mass- the mass of one mole of the compound in grams.

8. Monatomic Ions Chapter 7 Section 7.1 Chemical Names and Formulas
Many main-group elements (groups 1, ) can lose or gain electrons to form ions.
Ions formed from a single atom are known as monatomic ions.
Octet rule: Elements lose or gain electrons to have a the same electron configuration as a noble gas. (full outer energy level)
Some main-group elements tend to form covalent bonds instead of forming ions.
examples: carbon and silicon

9. Monatomic Ions, continued
Section 7.1 Chemical Names and Formulas Chemical Names and Formulas
Chapter 7
Monatomic Ions, continued
Naming Monatomic Ions
Monatomic cations (metals) take the element’s name.
examples:
K+ is called the potassium cation
Mg2+ is called the magnesium cation
Monatomic anions (nonmetals)- drop the end of the element’s name and add the ending “ide” to the root name.
F– is called the fluoride anion
N3– is called the nitride anion

10. Predicting ion charge of Main group elements
Elements lose or gain electrons according to the “octet” rule.
Elements want a full outer shell of electrons like a noble gas.
Group 1= lose 1 e-
Group 2 = 2+ lose 2 e-
Group 13 = 3+ lose 3e-
Group 14 = +4,-4 tend to share e-
Group 15 = -3 gain 3 e-
Group 16 = -2 gain 2 e-
Group 17 = -1 gain 1 e-
Group 18 = none (have full outer shell)

11. Section 1 Chemical Names and Formulas
Chapter 7
Common Monatomic Ions

12. Binary Ionic Compounds
Section 1 Chemical Names and Formulas
Chapter 7
Binary Ionic Compounds
Binary compounds- contain 2 different elements-a cation (metal) and an anion (nonmetal)
the total number of positive charges and negative charges must be equal- algebraically add up to zero
example: magnesium bromide
Ions combined: Mg2+, Br–, Br–
Chemical formula: MgBr2
Calcium oxide : Ions Ca2+, O2- = CaO
Lithium bromide: Ions Li1+, Br1- = LiBr

13. Binary Ionic Compounds, continued
Chapter 7
Section 1 Chemical Names and Formulas
Binary Ionic Compounds, continued
Formula for binary ionic compound- use “cross over” rule.
Write the ion formulas (cation first)
Write the ion charges
Cross the charges from top to bottom
Remove the charges
Simplify the numbers and remove the 1’s

14. Binary Ionic Compounds
Section 7.1 Chemical Names and Formulas
Chapter 7
Binary Ionic Compounds
example: aluminum oxide
Al3+
O2-
The correct formula is Al2O3
Always make sure the combined charges add up to zero
(2 × 3+) + (3 × 2–) = 0

15. Naming Binary Ionic Compounds
Section 7.1 Chemical Names and Formulas
Chapter 7
Naming Binary Ionic Compounds
The nomenclature, or naming system, for binary ionic compounds .
Cation name + anion name (ends in ide)
example: Al2O3 — aluminum oxide

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

17. Stock system - Binary ionic compounds
Some metals form cations that have more than one charge
A Roman numeral indicates the charge on the cation.
For example:
Copper = Cu1+ copper (I)
Cu2+ copper (II)
Iron = Fe2+ iron (II)
Fe3+ iron (III)
Mercury = Hg2+ = Mercury (II)
= Hg22+ = Mercury (I)

18. Stock system- Table

19. Section 1 Chemical Names and Formulas
Chapter 7
Common Monatomic Ions

20. Section 7.1 Chemical Names and Formulas
Chapter 7
Naming Binary Ionic Compounds- The Stock System of Nomenclature, continued
Sample Problem B
Write the formula and give the name for the compound formed by the ions Cr3+ and F–.

21. Sample Problem B Solution
Section 7.1 Stock system Names and Formulas
Chapter 7
Sample Problem B Solution
Write the symbols for the ions side by side. Write the cation first.
Cr3+ F−
Cross over the charges to give the lowest ratio of subscripts.
CrF3.
Chromium (III) fluoride

22. Polyatomic Ions Chapter 7
A group of shared atoms that carries a charge.
Ions that contain more than one element
Many are called oxyanions—they contain oxygen.
Some elements can combine with oxygen to form more than one type of oxyanion- come pairs.
For example: NO and NO3
nitrite and nitrate
The ion containing the lower number of oxygen atoms ends in “ite”

23. Chapter 7
The name of the ion that contains the greater number of oxygen atoms ends in “ate”.
SO42- = sulfate ion
The name of the ion that contains the smaller number of oxygen atoms ends in “ite”.
SO32- = sulfite ion

24. Ternary Compounds
Compounds containing 3 different elements- a metal cation and a polyatomic ion (oxyanion).
NaNO3
Na2SO4
MgSO4

25. Common polyatomic ions

26. Naming Compounds Containing Polyatomic Ions
Section 1 Chemical Names and Formulas
Naming Compounds Containing Polyatomic Ions
Click below to watch the Visual Concept.
Visual Concept

27. Name cation + name of the anion
Section Ternary compoundsChemical Names and Formulas
Write the formula for Aluminum sulfate
Write the formula for each ion Al3+ SO42-
Cross the charges over, bring down as subscripts and remove the charge sign.
Place the polyatomic ion in parenthesis ( )
when more than one ion is required.
Make sure the charges add up to zero.
Al2 (SO4)3
2 (3+) = 3 (-2)
(6+) (6-) = 0
Name the compound:
Name cation + name of the anion

28. Ternary compounds, continued
Write formulas and name the following ternary compounds made of the following ions:
Iron (III) and sulfite
Sodium and carbonate
Calcium and nitrite
Potassium and chlorate
Copper (II) and nitrate
Lead (IV) and oxalate
Magnesium and phosphate
Lithium and cyanide
Barium and hydroxide
Tin (II) and sulfate

29. Oyanions forming more than two diffferent ions
The ion that has one less oxygen than the “ite” ion begins with the prefix “hypo”
The ion that has one more oxygen than the “ate” ion, begins with the prefix “per”

30. Oyanions forming MORE than two diffferent ions, continued….
ClO- hypochlorite ion
ClO2- chlorite ion
ClO3- chlorate ion
ClO4- perchlorate ion
All ions in the series have the same charge.

31. Binary Molecular Compounds
MOLECULAR compounds are composed of individual covalently bonded units or molecules.
Binary molecular compounds are made up of 2 different nonmetals
A Prefix system is used to name and write formulas for binary molecular compounds.

32. Note:
The prefix mono
Is never used when there is only one atom of the first element in the chemical formula.

33. Prefixes for Naming Covalent Compounds
Section 1 Chemical Names and Formulas
Chapter 7
Prefixes for Naming Covalent Compounds

34. Naming Binary Molecular Compounds, continued
Section 1 Chemical Names and Formulas
Chapter 7
Naming Binary Molecular Compounds, continued
Sample Problem D
a. Give the name for As2O5.
Write the formula for oxygen difluoride.

35. Section 7.1 Acids Chemical Names and Formulas
Chapter 7
Acids and Salts
An acid is a molecular compound when dissolved in water releases H+ ions.
Binary acids contain two elements- hydrogen and a halogen (nonmetal)
Ternary or Oxyacids contain hydrogen + oxyanion

36. Naming Binary Acids Section 1 Chemical Names and Formulas
Click below to watch the Visual Concept.
Visual Concept

37. Naming Oxyacids Section 1 Chemical Names and Formulas
Click below to watch the Visual Concept.
Visual Concept

38. Prefixes and Suffixes for Oxyanions and Related Acids
Section 1 Chemical Names and Formulas
Prefixes and Suffixes for Oxyanions and Related Acids
Click below to watch the Visual Concept.
Visual Concept

39. Acids and Salts, continued
Section 1 Chemical Names and Formulas
Chapter 7
Acids and Salts, continued
An ionic compound composed of a cation and the anion from an acid is often referred to as a salt.
examples:
Table salt, NaCl, contains the anion from hydrochloric acid, HCl.
Calcium sulfate, CaSO4, is a salt containing the anion from sulfuric acid, H2SO4.
The bicarbonate ion, , comes from carbonic acid, H2CO3.

40. Salt Section 1 Chemical Names and Formulas
Click below to watch the Visual Concept.
Visual Concept

41. Lesson Starter Chapter 7 The chemical formula for water is H2O.
Section 3 Using Chemical Formulas
Chapter 7
Lesson Starter
The chemical formula for water is H2O.
How many atoms of hydrogen and oxygen are there in one water molecule?
How might you calculate the mass of a water molecule, given the atomic masses of hydrogen and oxygen?
In this section, you will learn how to carry out these and other calculations for any compound.

42. Section 3 Using Chemical Formulas
Chapter 7
Objectives
Calculate the formula mass or molar mass of any given compound.
Use molar mass to convert between mass in grams and amount in moles of a chemical compound.
Calculate the number of molecules, formula units, or ions in a given molar amount of a chemical compound.
Calculate the percentage composition of a given chemical compound.

43. Section 7.3 Using Chemical Formulas Using Chemical Formulas
Chapter 7
A chemical formula indicates:
the elements present in a compound
the relative number of atoms or ions of each element present in a compound
Chemical formulas also allow chemists to calculate:
formula mass
molar mass
percentage composition

44. average mass of H2O molecule: 18.02 amu
Section 7.3 Using Chemical Formulas
Chapter 7
Formula Mass-review
The formula mass of any molecule, formula unit, or ion is the sum of the average atomic masses of all atoms represented in its formula.
example: formula mass of water, H2O
average atomic mass of H: 1.01 amu
average atomic mass of O: amu
average mass of H2O molecule: amu

45. Section 7.3 Using Chemical Formulas
Molar Masses- review
Chapter 7
The molar mass of a substance is equal to the mass in grams of one mole, or approximately × 1023 particles, of the substance.
The molar mass (g) = atomic mass or formula mass expressed in g/mol.

46. Calculating Molar Masses for Ionic Compounds
Section 3 Using Chemical Formulas
Chapter 7
Calculating Molar Masses for Ionic Compounds

47. Molar Mass as a Conversion Factor
Section 3 Using Chemical Formulas
Chapter 7
Molar Mass as a Conversion Factor
The molar mass of a compound can be used as a conversion factor to relate an amount in moles to a mass in grams for a given substance.

48. Mole-Mass Calculations
Section 3 Using Chemical Formulas
Chapter 7
Mole-Mass Calculations

49. Molar Mass as a Conversion Factor, continued
Section 3 Using Chemical Formulas
Chapter 7
Molar Mass as a Conversion Factor, continued
Sample Problem:
What is the mass in grams of 2.50 mol of Carbon dioxide gas?

50. Percentage Composition
Section 3 Using Chemical Formulas
Chapter 7
Percentage Composition
It is often useful to know the percentage by mass of a particular element in a chemical compound.
The mass percentage of an element in a compound is the same regardless of the sample’s size.

51. Percentage Composition, continued
Section 3 Using Chemical Formulas
Chapter 7
Percentage Composition, continued
The percentage by mass of each element in a compound is known as the percentage composition of the compound.
% element in compound= mass of the element x 100%
total mass of compound
(formula mass)
The mass percentage of an element in a compound is the same regardless of the sample’s size.

52. Percentage Composition of Iron Oxides
Section 3 Using Chemical Formulas
Chapter 7
Percentage Composition of Iron Oxides

53. Percentage Composition, continued
Section 3 Using Chemical Formulas
Chapter 7
Percentage Composition, continued
Sample Problem:
Find the percentage composition of copper(I) sulfide, Cu2S.

54. Section 4 Determining Chemical Formulas
Chapter 7
Lesson Starter
Compare and contrast models of the molecules NO2 and N2O4.
The numbers of atoms in the molecules differ, but the ratio of N atoms to O atoms for each molecule is the same.

55. Section 4 Determining Chemical Formulas
Chapter 7
Objectives
Define empirical formula, and explain how the term applies to ionic and molecular compounds.
Determine an empirical formula from either a percentage or a mass composition.
Explain the relationship between the empirical formula and the molecular formula of a given compound.
Determine a molecular formula from an empirical formula.

56. Empirical and Actual Formulas
Section 4 Determining Chemical Formulas
Chapter 7
Empirical and Actual Formulas

57. Section 4 Determining Chemical Formulas
Chapter 7
An empirical formula is the smallest whole number ratio of elements (subscripts) in the compound.
For an ionic compound, the formula unit is the compound’s empirical formula-it is the simplest ratio of ions

58. Empirical and Molecular Formulas
For a molecular compound- the empirical formula does not necessarily indicate the actual numbers of atoms present in each molecule.
example: the empirical formula of the gas diborane is BH3, but the molecular formula is B2H6.

59. Calculation of Empirical Formulas
Section 4 Determining Chemical Formulas
Calculation of Empirical Formulas
Chapter 7
Finding the empirical formula from percent composition
1. Assume you have a 100g sample
2. Convert % to grams of each element
3. Convert mass of each element to moles
4. Divide each number of moles by the
smaller number of moles in the ratio
5. These small whole numbers represent the
subscripts in the empirical formula
If mass of each element is known, begin with
step 3.

60. Finding empirical formula from % composition
The percentage composition is 78.1% B and 21.9% H.
g of diborane contains 78.1 g of B and 21.9 g of H.
g B x 1 mole/ 10.81g = 7.22 mole B
21.9 g H x 1 mole/ 1.01gH = 21.7 mol H
mole B = 1mole B mol H = 3.01 moleH
4. Empirical formula = BH3
Subscripts represent mole ratios of elements in 1 mole of the compound- the ratios should be close to a whole number.

61. Calculation of Empirical Formulas, continued
Section 4 Determining Chemical Formulas
Chapter 7
Calculation of Empirical Formulas, continued
Sample Problem :
A compound contains 32.38% sodium, 22.65% sulfur, and 44.99% oxygen. Find the empirical formula of this compound.

62. Calculation of Molecular Formulas
Section 4 Determining Chemical Formulas
Calculation of Molecular Formulas
Chapter 7
The empirical formula = the smallest possible whole number ratio of elements in a compound
The molecular formula = the actual formula of a molecular compound.
An empirical formula may or may not be a correct molecular formula.
The relationship between a compound’s empirical formula and its molecular formula is: x(empirical formula) = molecular formula

63. Calculation of Molecular Formulas
Section 4 Determining Chemical Formulas
Chapter 7
Calculation of Molecular Formulas
The formula masses have a similar relationship.
x(empirical formula mass) = molecular formula mass
Dividing the experimental formula mass by the empirical formula mass gives the value of x.
X= how much larger the molecular formula is compared to the empirical. It’s always a small whole number multiple.
Molecular mass of the compound must be known.

64. Comparing Empirical and Molecular Formulas
Section 4 Determining Chemical Formulas
Chapter 7
Comparing Empirical and Molecular Formulas

65. Calculation of Molecular Formulas, continued
Section 4 Determining Chemical Formulas
Chapter 7
Calculation of Molecular Formulas, continued
Sample Problem:
The empirical formula of a compound of phosphorus and oxygen is P2O5. The molar mass of this compound is g/mol. What is the compound’s molecular formula?