1. Unit 1: Structure of Matter
Sections: 1.4, 2.5, 2.6,
urea
Chalcopyrite.
Elemental sulfur (S8) consists of eight S atoms joined in a ring.
A scientific research helium balloon.
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2. Classifications of Matter

3. Chemistry is the study of matter and the changes it undergoes.
Matter is anything that occupies space and has mass.
A substance is a form of matter that has a definite composition and distinct properties.
liquid nitrogen
gold ingots
silicon crystals

4. An element is a substance that cannot be separated into simpler substances by chemical means.
114 elements have been identified
82 elements occur naturally on Earth
gold, aluminum, lead, oxygen, carbon, sulfur
32 elements have been created by scientists
technetium, americium, seaborgium

6. Atomic mass is the mass of an atom in atomic mass units (amu)
Micro World
atoms & molecules
Macro World
grams
Atomic mass is the mass of an atom in atomic mass units (amu)
By definition:
1 atom 12C “weighs” 12 amu
On this scale
1H = amu
16O = amu

7. The average atomic mass is the weighted
average of all of the naturally occurring
isotopes of the element.

8. 3.1
Copper, a metal known since ancient times, is used in electrical cables and pennies, among other things.
The atomic masses of its two stable isotopes, (69.09 percent) and (30.91 percent), are amu and amu, respectively.
Calculate the average atomic mass of copper. The relative abundances are given in parentheses.

9. Average atomic mass (63.55)

10. Avogadro’s number (NA)
The Mole (mol): A unit to count numbers of particles
Dozen = 12
Pair = 2
The mole (mol) is the amount of a substance that
contains as many elementary entities as there
are atoms in exactly grams of 12C
1 mol = NA = x 1023
Avogadro’s number (NA)

11. Molar mass is the mass of 1 mole of in grams marbles atoms
eggs
shoes
Molar mass is the mass of 1 mole of in grams
marbles
atoms
1 mole 12C atoms = x 1023 atoms = g
1 12C atom = amu
1 mole lithium atoms = g of Li
For any element
atomic mass (amu) = molar mass (grams)

12. One Mole of: S C Hg Cu Fe

13. 1 12C atom
12.00 amu
12.00 g
6.022 x C atoms =
1.66 x g
1 amu x
1 amu = 1.66 x g or 1 g = x 1023 amu
M = molar mass in g/mol
NA = Avogadro’s number

14. 3.2
Helium (He) is a valuable gas used in industry, low-temperature research, deep-sea diving tanks, and balloons.
How many moles of He atoms are in 6.46 g of He?

15. 3.3
Zinc (Zn) is a silvery metal that is used in making brass (with copper) and in plating iron to prevent corrosion.
How many grams of Zn are in mole of Zn?

16. 3.4 Sulfur (S) is a nonmetallic element that is present in coal.
When coal is burned, sulfur is converted to sulfur dioxide and eventually to sulfuric acid that gives rise to the acid rain phenomenon.
How many atoms are in 16.3 g of S?

17. A compound is a substance composed of atoms of two or more elements chemically united in fixed proportions.
Compounds can only be separated into their pure components (elements) by chemical means.
lithium fluoride
quartz
dry ice – carbon dioxide

18. Molecular Compound
H2O
NH3
CO2
HCl CO
Binary Molecular Compound

19. 2.8 Write chemical formulas for the following molecular compounds:
carbon disulfide
(b) disilicon hexabromide

20. Ionic compounds consist of a combination of cations and anions.
The formula is usually the same as the empirical formula.
The sum of the charges on the cation(s) and anion(s) in each formula unit must equal zero.

21. cation – ion with a positive charge
An ion is an atom, or group of atoms, that has a net positive or negative charge.
cation – ion with a positive charge
If a neutral atom loses one or more electrons
it becomes a cation. Na
11 protons
11 electrons
Na+
11 protons
10 electrons
anion – ion with a negative charge
If a neutral atom gains one or more electrons
it becomes an anion.
Cl-
17 protons
18 electrons Cl
17 protons
17 electrons

22. A monatomic ion contains only one atom:
Na+, Cl-, Ca2+, O2-, Al3+, N3-
A polyatomic ion contains more than one atom:
OH-, CN-, NH4+, NO3-

23. Formulas of Ionic Compounds
2 x +3 = +6
3 x -2 = -6
Al2O3
Al3+
O2-
1 x +2 = +2
2 x -1 = -2
CaBr2
Ca2+
Br-
2 x +1 = +2
1 x -2 = -2
Na2CO3
Na+
CO32-

24. The most reactive metals (green) and the most reactive nonmetals (blue) combine to form ionic compounds.

25. Common Ions Shown on the Periodic Table

26. 2.4
Write the formula of magnesium nitride, containing the Mg2+ and N3− ions.

27. 2.6 Write chemical formulas for the following compounds:
mercury(I) nitrite
cesium sulfide
calcium phosphate

28. formula mass (amu) = molar mass (grams)
Formula mass is the sum of the atomic masses
(in amu) in a formula unit of an ionic compound.
NaCl
1Na
22.99 amu
1Cl
amu
NaCl
58.44 amu
For any ionic compound
formula mass (amu) = molar mass (grams)
1 formula unit NaCl = amu
1 mole NaCl = g NaCl

29. Concept Review
Identify whether the following diagrams represent (a) an element or (b) a compound? Each color sphere (or truncated sphere) represents an atom.

30. A diatomic molecule contains only two atoms:
A molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical forces. H2
H2O
NH3
CH4
A diatomic molecule contains only two atoms:
diatomic elements
H2, N2, O2, Br2, HCl, CO
A polyatomic molecule contains more than two atoms:
O3, H2O, NH3, CH4

31. Molecules
Diatomic
HCl CO

32. Molecules
Polyatomic O3
H2O
CO2
NH3

33. molecular mass (amu) = molar mass (grams)
Molecular mass (or molecular weight) is the sum of
the atomic masses (in amu) in a molecule.
SO2 1S
32.07 amu 2O
+ 2 x amu
SO2
64.07 amu
For any molecule
molecular mass (amu) = molar mass (grams)
1 molecule SO2 = amu
1 mole SO2 = g SO2

34. 3.5
Calculate the molecular masses (in amu) of the following compounds:
sulfur dioxide (SO2), a gas that is responsible for acid rain
caffeine (C8H10N4O2), a stimulant present in tea, coffee, and cola beverages

35. 3.6 Methane (CH4) is the principal component of natural gas.
How many moles of CH4 are present in 6.07 g of CH4?

36. 3.7
How many hydrogen atoms are present in 25.6 g of urea [(NH2)2CO], which is used as a fertilizer, in animal feed, and in the manufacture of polymers?
The molar mass of urea is g.

37. Percent composition of an element in a compound =
n x molar mass of element
molar mass of compound
x 100%
n is the number of moles of the element in 1 mole of the compound
%C =
2 x (12.01 g)
46.07 g
x 100% = 52.14%
C2H6O
%H =
6 x (1.008 g)
46.07 g
x 100% = 13.13%
%O =
1 x (16.00 g)
46.07 g
x 100% = 34.73%
52.14% % % = 100.0%

38. 3.8
Phosphoric acid (H3PO4) is a colorless, syrupy liquid used in detergents, fertilizers, toothpastes, and in carbonated beverages for a “tangy” flavor.
Calculate the percent
composition by mass of H, P, and O in this compound.

39. 3.10 Chalcopyrite (CuFeS2) is a principal mineral of copper.
Calculate the number of kilograms of Cu in × 103 kg of chalcopyrite.

40. Formulas and Models

41. A molecular formula shows the exact number of atoms of each element in the smallest unit of a substance.
An empirical formula shows the simplest
whole-number ratio of the atoms in a substance.
H2O
molecular
empirical
H2O
CH2O
C6H12O6 O O3
NH2
N2H4
C2H5
C4H10
Butane

42. 2.2
Write the molecular formula of methanol, an organic solvent and antifreeze, from its ball-and-stick model, shown below.

43. 2.3 Write the empirical formulas for the following molecules:
acetylene (C2H2), which is used in welding torches
glucose (C6H12O6), a substance known as blood sugar
nitrous oxide (N2O), a gas that is used as an anesthetic gas (“laughing gas”) and as an aerosol propellant for whipped creams.

44. Percent Composition and Empirical Formulas
Steps:
Percent to mass
Mass to moles
Divide by small
Multiply ‘til whole

45. 3.9 Ascorbic acid (vitamin C) cures scurvy.
It is composed of percent carbon (C), 4.58 percent hydrogen (H), and percent oxygen (O) by mass.
Determine its empirical formula.

46. Combustion Analysis g CO2 mol CO2 mol C g C 6.0 g C = 0.5 mol C g H2O
Combust 11.5 g ethanol
Collect 22.0 g CO2 and 13.5 g H2O
g CO2
mol CO2
mol C
g C
6.0 g C = 0.5 mol C
g H2O
mol H2O
mol H
g H
1.5 g H = 1.5 mol H
g of O = g of sample – (g of C + g of H)
4.0 g O = 0.25 mol O
Empirical formula C0.5H1.5O0.25
Divide by smallest subscript (0.25)
Empirical formula C2H6O

47. Hydrate Steps: Find the mass of water or mass of anhydrate
Turn mass of water and mass of anhydrate into moles (individually)
Find the mole ratio; mole of anhydrate mole of water
mole of anhydrate mole of anhydrate
Write the formula of the hydrate :

48. Example
A calcium chloride hydrate has a mass of 4.72 g. After heating for several minutes the mass of the anhydrate is found to be 3.56 g. Use this information to determine the formula for the hydrate.

49. Molecular Formula Steps: Find empirical formula
Determine the molar mass of the empirical formula
Find multiplier (molar mass given/empirical molar mass)
Multiply empirical formula subscripts by the multiplier

50. 3.11
A sample of a compound contains percent nitrogen and percent oxygen by mass, as determined by a mass spectrometer.
In a separate experiment, the molar mass of the compound is found to be between 90 g and 95 g.
Determine the molecular formula and the accurate molar mass of the compound.

51. Allotrope one of two or more distinct forms of an element.
different number of atoms of the element
different properties physical and chemical properties

52. A mixture is a combination of two or more substances in which the substances retain their distinct identities.
Homogenous mixture – composition of the mixture is the same throughout
soft drink, milk, solder
Heterogeneous mixture – composition is not uniform throughout
cement,
iron filings in sand

53. Mass Spectrometry
Heavy
Light
Mass Spectrum of Ne

54. Light
Mass Spectrum of Ne
Heavy