Dr. Paul CharlesworthMichigan Technological UniversityDr. Paul Charlesworth

Michigan Technological University

C h a p t e rC h a p t e r

Chemistry, 4th EditionMcMurry/Fay

Chemistry, 4th EditionMcMurry/Fay

22Atoms, Molecules, and IonsAtoms, Molecules, and Ions

Chapter 02 Slide 2Prentice Hall ©2004

Conservation of MassConservation of Mass

Chapter 02 Slide 3Prentice Hall ©2004

Dalton’s Atomic Theory 01Dalton’s Atomic Theory 01

• Robert Boyle (1627–1691): Provided evidence for the atoms and defined the nature of an element.

• Joseph Priestley (1733–1804): Isolated oxygen gas from decomposition of mercury(II) oxide.

• Antoine Lavoisier (1743–1794): Showed that mass of products is exactly equal to the mass of reactants.

Chapter 02 Slide 4Prentice Hall ©2004

Dalton’s Atomic Theory 02Dalton’s Atomic Theory 02

• Law of Mass Conservation: Mass is neither

created nor destroyed in chemical reactions.

• Law of Definite Proportions: Different samples of

a pure chemical substance always contain the

same proportion of elements by mass.

Chapter 02 Slide 5Prentice Hall ©2004

Dalton’s Atomic Theory 03Dalton’s Atomic Theory 03

• John Dalton (1766–1844): Proposed explanations

for the laws of mass conservation and definite

proportions.

Flash Animation - Click to ContinueFlash Animation - Click to ContinueFlash Animation - Click to ContinueFlash Animation - Click to Continue

Chapter 02 Slide 6Prentice Hall ©2004

Dalton’s Atomic Theory 04Dalton’s Atomic Theory 04

Chapter 02 Slide 7Prentice Hall ©2004

• Law of Multiple Proportions: • When two elements form two different compounds, the mass ratios are related by small whole numbers.

Dalton’s Atomic Theory 04Dalton’s Atomic Theory 04

Chapter 02 Slide 8Prentice Hall ©2004

Dalton’s Atomic Theory 05Dalton’s Atomic Theory 05

• Nitrogen & oxygen combine to form NO or NO2:

• In NO the N:O mass ratio is 7:8

• In NO2 the N:O mass ratio is 7:16

• Hydrogen & oxygen combine to form H2O or H2O2:

• In H2O the H:O mass ratio is 1:8

• In H2O2 the H:O mass ratio is 1:16

Chapter 02 Slide 9Prentice Hall ©2004

Dalton’s Atomic Theory 06Dalton’s Atomic Theory 06

• Methane and ethane are both constituents of

natural gas. A sample of methane contains 11.40 g

of carbon and 3.80 g of hydrogen, whereas a

sample of ethane contains 4.47 g of carbon and

1.118 g of hydrogen. Show that the two substances

obey the law of multiple proportions.

Chapter 02 Slide 10Prentice Hall ©2004

The Structure of Atoms 01The Structure of Atoms 01

• Cathode-Ray Tube (Thomson, 1856–1940):

• Cathode rays

consist of tiny

negatively

charged particles,

now called

electrons.

Chapter 02 Slide 11Prentice Hall ©2004

The Structure of Atoms 02The Structure of Atoms 02

• Deflection of electron depends on three factors:

• Strength of electric or magnetic field

• Size of negative charge on electron

• Mass of the electron

• Thomson calculated the electron’s charge to mass

ratio as 1.758820 x 108 Coulombs per gram.

Chapter 02 Slide 12Prentice Hall ©2004

The Structure of Atoms 03The Structure of Atoms 03

• Oil Drop Experiment (Millikan, 1868–1953): Applied a voltage to oppose the downward fall of charged drops and suspend them.

• Voltage on plates place 1.602176 x 10-19 C of charge on each oil drop.

• Millikan calculated the electron’s mass as 9.109382 x 10-28 grams.

Chapter 02 Slide 13Prentice Hall ©2004

• Discovery of Nucleus (Rutherford, 1871 – 1937):• Rutherford irradiated

gold foil with a beamof alpha () particlesto search for positivecharged particles.

The Structure of Atoms 05The Structure of Atoms 05

Chapter 02 Slide 14Prentice Hall ©2004

Discovery of Nucleus (Rutherford, 1871–1937):Rutherford irradiatedgold foil with a beamof alpha () particlesto search for positivecharged particles.

Atom must be mostly empty space except for a central positive mass concentration.

The Structure of Atoms 05The Structure of Atoms 05

Chapter 02 Slide 15Prentice Hall ©2004

The Structure of Atoms 04The Structure of Atoms 04

• Structure of the Atom:

Chapter 02 Slide 16Prentice Hall ©2004

The Structure of Atoms 05The Structure of Atoms 05

Chapter 02 Slide 17Prentice Hall ©2004

The Structure of Atoms 06The Structure of Atoms 06

• Isotopes: Atoms with identical atomic numbers, but different mass numbers.

• Average Isotopic Mass: A weighted average of the isotopic masses of an element’s naturally occurring isotopes.

• Atomic Mass: A weighted average of the isotopic masses of an element’s naturally occurring isotopes.

Chapter 02 Slide 18Prentice Hall ©2004

The Structure of Atoms 07The Structure of Atoms 07

• The isotope is used medically for diagnosis of

pancreatic disorders. How many protons, neutrons,

and electrons does an atom of have?

• An atom of element X contains 47 protons and 62

neutrons. Identify the element, and write the

symbol for the isotope in the standard format.

7534Se

7534Se

Chapter 02 Slide 19Prentice Hall ©2004

The Structure of Atoms 08The Structure of Atoms 08

• Chlorine has two naturally occurring isotopes:

with an abundance of 75.77% and an isotopic mass

of 34.969 amu, and with an abundance of

24.23% and an isotopic mass of 36.966 amu. What

is the atomic mass of chlorine?

3717 Cl

3517 Cl

Chapter 02 Slide 20Prentice Hall ©2004

Compounds and Mixtures 01Compounds and Mixtures 01

Chapter 02 Slide 21Prentice Hall ©2004

Compounds and Mixtures 02Compounds and Mixtures 02

Chapter 02 Slide 22Prentice Hall ©2004

Atoms, Molecules, and Ions 01Atoms, Molecules, and Ions 01

• Covalent Bonding (Molecules): The most common type of chemical bond is formed when two atoms share some of their electrons.

Chapter 02 Slide 23Prentice Hall ©2004

Atoms, Molecules, and Ions 02Atoms, Molecules, and Ions 02

• Ionic Bonding (Ionic Solids): These are formed by a transfer of one or more electrons from one atom to another.

Chapter 02 Slide 24Prentice Hall ©2004

Atoms, Molecules, and Ions 03Atoms, Molecules, and Ions 03

• Which of the following drawings represents an ionic compound, and which a molecular compound?

Chapter 02 Slide 25Prentice Hall ©2004

Atoms, Molecules, and Ions 04Atoms, Molecules, and Ions 04

• Naming Binary Ionic Compounds:

• Identify the positive ion and then the negative ion.

• The positive ion uses its elemental name.

• The negative ion substitutes the second half of its elemental name with –ide.

• Do not use Greek prefixes such as mono–, di–, or tri–.

Chapter 02 Slide 26Prentice Hall ©2004

Atoms, Molecules, and Ions 05Atoms, Molecules, and Ions 05

Chapter 02 Slide 27Prentice Hall ©2004

Atoms, Molecules, and Ions 06Atoms, Molecules, and Ions 06

Chapter 02 Slide 28Prentice Hall ©2004

Atoms, Molecules, and Ions 07Atoms, Molecules, and Ions 07

• Main Group Cations and Anions.

Ions combine to form neutral compounds.

Examples:

Na+ and Cl– combine to form NaCl.

Ca2+ and Cl– combine to form CaCl2.

Al3+ and Cl– combine to form AlCl3.

Chapter 02 Slide 29Prentice Hall ©2004

Atoms, Molecules, and Ions 08Atoms, Molecules, and Ions 08

Chapter 02 Slide 30Prentice Hall ©2004

Atoms, Molecules, and Ions 09Atoms, Molecules, and Ions 09

• Naming Binary Molecular Compounds:• The more cationlike element uses its elemental name.

• The more anionlike element substitutes the second half of its elemental name with –ide.

• Use the Greek prefixes to express the number of each element present.

Chapter 02 Slide 31Prentice Hall ©2004

Atoms, Molecules, and Ions 10Atoms, Molecules, and Ions 10

Chapter 02 Slide 32Prentice Hall ©2004

Atoms, Molecules, and Ions 11Atoms, Molecules, and Ions 11

• If the green spheres represent cations, and the blue

represent anions, which of the formulas are

consistent with the figure?

(a) LiBr

(b) NaNO2

(c) CaCl2

(d) K2CO3

(e) Fe2(SO4)3

Chapter 02 Slide 33Prentice Hall ©2004

Atoms, Molecules, and Ions 12Atoms, Molecules, and Ions 12

Chapter 02 Slide 34Prentice Hall ©2004

Atoms, Molecules, and Ions 13Atoms, Molecules, and Ions 13

• Name the following acids:

(a) HBrO(aq)

(b) HCN(aq)

(c) HIO4(aq)

(d) HBrO2(aq)

(e) H2CrO4(aq)