Transcript Atoms. Molecules, and Ions

Chapter
2
Atoms, Molecules, and Ions
Chemistry, 4th Edition
McMurry/Fay
Dr. Paul Charlesworth
Michigan Technological University
Atomic 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 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.
3
Joseph 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 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 Mass
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Conservation of Mass
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Atomic Theory
•
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 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 Proportions
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Atomic Theory
•
•
Nitrogen & oxygen combine to form NO or NO2:
•
In NO the N:O mass ratio is 7:8
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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 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 Proportions
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Dalton’s Atomic Theory
•
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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Dalton’s Atomic Theory
•
John Dalton (1766–1844): Proposed explanations for the
laws of mass conservation and definite proportions.
Postulate #2
•
All atoms of a given element are identical
having the element’s unique properties
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Dalton’s Atomic Theory
•
John Dalton (1766–1844): Proposed explanations for the
laws of mass conservation and definite proportions.
Postulate #3
•
Atoms are neither created nor destroyed in
chemical reactions
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Dalton’s Atomic Theory
•
John Dalton (1766–1844): Proposed explanations for the
laws of mass conservation and definite proportions.
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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Dalton’s Atomic Theory
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Dalton’s Atomic Theory
•
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 Proportions
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Dalton’s Atomic Theory
•
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.
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The Structure of Atoms
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The Structure of Atoms
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The Structure of Atoms
•
Cathode-Ray Tube (Thomson, 1856–1940):
•
Cathode rays
consist of tiny
negatively
charged particles,
now called
electrons.
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The Structure of Atoms
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The Structure of Atoms
•
•
Deflection of electron depends on three factors:
•
Strength of electric or magnetic field
•
Size of negative charge on electron
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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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The Structure of Atoms
•
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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The Structure of Atoms
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The Structure of Atoms
•
Discovery of Nucleus (Rutherford, 1871 – 1937):
•
Rutherford irradiated
gold foil with a beam
of alpha () particles
to search for positive
charged particles.
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The Structure of Atoms
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The Structure of Atoms
Discovery of Nucleus (Rutherford, 1871–1937):
Rutherford irradiated
gold foil with a beam
of alpha () particles
to search for positive
charged particles.
Atom must be mostly
empty space except
for a central positive
mass concentration.
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The Structure of Atoms
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The Structure of Atoms
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The Structure of Atoms
•
Structure of the Atom:
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The Structure of Atoms
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The Structure of Atoms
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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The Structure of Atoms
•
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 Structure of Atoms
•
The isotope
75
34Se
is used medically for diagnosis of
pancreatic disorders. How many protons, neutrons,
and electrons does an atom of
•
75
34Se
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.
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The Structure of Atoms
•
Chlorine has two naturally occurring isotopes: 35
17 Cl
with an abundance of 75.77% and an isotopic mass
of 34.969 amu, and
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17 Cl
with an abundance of
24.23% and an isotopic mass of 36.966 amu. What
is the atomic mass of chlorine?
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The Structure of Atoms
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Compounds and Mixtures
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Ions
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Electrically charged atom or group of atoms
Cation:
• Anion:
•
•
(+) charge
(-) charge
Ionic Compound: A compound that consists of ions
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Ions
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Ions
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Atoms, Molecules, and Ions
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Atoms, Molecules, and Ions
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Naming Cations
1. Elements having just one characteristic ionic
charge
Simply use the name of the element:
Na+ sodium ion
K+
potassium ion
Ca2+ calcium ion
Zn2+
Al3+
etc.
zinc ion
aluminum ion
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Naming 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
Fe3+ iron (III) ion
Pb2+ lead (II) ion
Pb4+ lead (IV) ion
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Naming Anions
Stem + ide
FClBrO2S2N3-
fluoride
chloride
bromide
oxide
sulfide
nitride
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Naming 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 Oxoanions
(NO3)(NO2)(SO4)2(SO3)2(PO4)3(CO3)2OH-
nitrate
nitrite
sulfate
sulfite
phosphate
carbonate
hydroxide
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Some Common Oxoanions
Dichromate
(Cr2O7)2-
Permanganate
(MnO4)-
Hydrogen Carbonate
(HCO3)-
Bromate
(BrO3)-
Chlorate
(ClO3)-
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Polyatomic Ions
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Ionic 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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Ionic Compounds
•
Which of the following drawings represents an ionic
compound, and which a molecular compound?
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Ionic Compounds
•
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 Compounds
Combine Ion Names
Cation + Anion
NaCl
CuCl
CuCl2
CaCO3
Al2O3
sodium chloride
copper (I) chloride
copper (II) chloride
calcium carbonate
aluminum oxide
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Naming 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 Oxoacids
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Molecules
•
Covalent Bonding (Molecules): The most
common type of chemical bond is formed when two
atoms share some of their electrons.
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Molecules
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Molecules and Compounds
•
Molecule: A definite and distinct group of bonded
atoms
•
Molecular compound: A compound consisting of
molecules
•
Molecular formula:
•
Molecular Weight (MW): The average mass of
one of the molecules of a compound.
Water → H20
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Naming Molecular Compounds
MUCH more complicated!
Binary compounds are often named as if they were
ionic:
HCl
CO2
hydrogen chloride
carbon dioxide
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The Alkanes
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The Alkanes
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Other Interesting Compounds
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Other Interesting Compounds
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