Dr. Paul Charlesworth Michigan Technological University Dr. Paul Charlesworth Michigan Technological University C h a p t e rC h a p t e r C h a p t e

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

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Atomic TheoryAtomic Theory

• Robert Boyle (1627–1691)

• Joseph Priestley (1733–1804)

• Antoine Lavoisier (1743–1794)

• Joseph Proust (1754–1826)

• John Dalton (1766-1844)

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Robert BoyleRobert Boyle

• Robert Boyle (1627–1691): Provided evidence for the atoms and defined the nature of an element. More than anyone else, invented the modern experimental method.

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Joseph PriestlyJoseph Priestly

• Joseph Priestley (1733–1804): Isolated oxygen gas from decomposition of mercury(II) oxide. Identified 8 new gases (more than anyone else). Minister. Revolutionary.

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Antoine LavoisierAntoine Lavoisier

Antoine Lavoisier (1743–1794): Showed that mass of products is exactly equal to the mass of reactants. Father of modern chemistry. Metric system. Beheaded during the revolution.

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Conservation of MassConservation of Mass

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Conservation of MassConservation of Mass

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• 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.

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Joseph Louis ProustJoseph Louis Proust

Joseph Louis Proust (1754–1826): Proved the law of definite proportions (sometimes called Proust’s Law). Father was an apothecary. Discovered 3 vegetable sugars.

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Law of Definite ProportionsLaw of Definite Proportions

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• 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

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Dalton’s Atomic TheoryDalton’s Atomic Theory

• John Dalton (1766–

1844): Proposed

explanations for the laws

of mass conservation

and definite proportions.

Provided a unified atomic

theory. Avid

meteorologist. Worked

with Nitrous Oxide and

Nitrogen Dioxide.

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Law of Multiple ProportionsLaw of Multiple Proportions

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• John Dalton (1766–1844): Proposed explanations for the

laws of mass conservation and definite proportions.

Postulate #1

• Elements are composed of tiny particles

called atoms

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Postulate #2

• All atoms of a given element are identical

having the element’s unique properties

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Postulate #3

• Atoms are neither created nor destroyed in

chemical reactions

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Postulate #4

• Compounds are formed when atoms of more

than one elenment combine. A given compound

always has the same relative numbe of atoms

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


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Law of Multiple ProportionsLaw of Multiple Proportions

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• Methane and ethane are both constituents of natur

al gas. A sample of methane contains 11.40 g of ca

rbon and 3.80 g of hydrogen, whereas a sample of

ethane contains 4.47 g of carbon and 1.118 g of hy

drogen. Show that the two substances obey the law

of multiple proportions.

http://www.wfu.edu/chemistry/courses/jonesbt/111/Chapter2/multiple.xls






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The Structure of AtomsThe Structure of Atoms

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24


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

• Cathode rays

consist of tiny

negatively

charged particles,

now called

electrons.

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27


• 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.

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• 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.

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

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


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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.


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34


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• Structure of the Atom:

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Atomic Mass Unit

1 amu = 1/12 of the mass of on atom of Carbon-12

1 amu = 1.6605 x 10-24 g

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

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

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• 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

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• 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

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Compounds and MixturesCompounds and Mixtures

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IonsIons

• Electrically charged atom or group of atoms

• Cation: (+) charge• Anion: (-) charge

• Ionic Compound: A compound that consists of ions

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IonsIons

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IonsIons

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Atoms, Molecules, and IonsAtoms, Molecules, and Ions

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Atoms, Molecules, and IonsAtoms, Molecules, and Ions

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Naming CationsNaming Cations

1. Elements having just one characteristic ionic charge

Simply use the name of the element:

Na+ sodium ion Zn2+ zinc ionK+ potassium ion Al3+ aluminum

ionCa2+ calcium ion etc.

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Naming CationsNaming Cations

2. Elements forming more than one type of cation

Follow the name of the element with its stock number (Roman numeral equal to the number of electrons lost):

Fe2+ iron (II) ion Pb2+ lead (II) ionFe3+ iron (III) ion Pb4+ lead (IV) ion

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Naming AnionsNaming Anions

Stem + ide

F- fluorideCl- chlorideBr- bromideO2- oxideS2- sulfideN3- nitride

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Naming OxoanionsNaming Oxoanions

Stem + ate

If more than one combination exits:

Stem + ate → larger number of O atoms

Stem + ite → smaller number of O atoms

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Some Common OxoanionsSome Common Oxoanions

(NO3)- nitrate

(NO2)- nitrite

(SO4)2- sulfate

(SO3)2- sulfite

(PO4)3- phosphate

(CO3)2- carbonate

OH- hydroxide

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Some Common OxoanionsSome Common Oxoanions

Dichromate (Cr2O7)2-

Permanganate (MnO4)-

Hydrogen Carbonate (HCO3)-

Bromate (BrO3)-

Chlorate (ClO3)-

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Polyatomic IonsPolyatomic Ions

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Ionic CompoundsIonic Compounds

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

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

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• 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.

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Naming Ionic CompoundsNaming Ionic Compounds

Combine Ion NamesCation + Anion

NaCl sodium chlorideCuCl copper (I) chlorideCuCl2 copper (II) chloride

CaCO3 calcium carbonate

Al2O3 aluminum oxide

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Naming Ionic CompoundsNaming Ionic Compounds

• 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

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Common OxoacidsCommon Oxoacids

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MoleculesMolecules

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

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MoleculesMolecules

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• Molecule: A definite and distinct group of bonded atoms

• Molecular compound: A compound consisting of molecules

• Molecular formula: Water → H20

• Molecular Weight (MW): The average mass of one of the molecules of a compound.

Molecules and CompoundsMolecules and Compounds

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Naming Molecular CompoundsNaming Molecular Compounds

MUCH more complicated!

Binary compounds are often named as if they were ionic:

HCl hydrogen chlorideCO2 carbon dioxide

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The AlkanesThe Alkanes

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The AlkanesThe Alkanes

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Other Interesting CompoundsOther Interesting Compounds

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Other Interesting CompoundsOther Interesting Compounds

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Dr. Paul Charlesworth Michigan Technological University Dr. Paul Charlesworth Michigan Technological University C h a p t e rC h a p t e r C h a p t e