Transcript Figure 1.01a: (a.)The surface of a single grain of table salt.

Chapter 2:
ATOMS, MOLECULES, AND IONS
The Early History of Chemistry

Before 16th Century
–Greeks: 4 fundamental substances: fire, earth, water, and air.
–Alchemy: Attempts (scientific or otherwise) to change cheap
metals into gold.

17th Century
–Robert Boyle: First “chemist” to perform quantitative
experiments to measure the relationship between pressure and
volume. Define chemical elements: substance cannot further break
down.

18th Century
–George Stahl: Phlogiston flows out of a burning material.
–Joseph Priestley: Discovers oxygen gas, “dephlogisticated air.”
“The Priestley Award” of Am. Chem. Soc.
Law of Conservation of Mass

Discovered by Antoine Lavoisier

Combustion involves oxygen, not phlogiston

Mass is neither created nor destroyed
In 1789 Lavoisier published the 1st modern chem. textbook:
“Elementary Treatise on chemistry”
Other Fundamental Chemical Laws
Law of Definite Proportion
(Joseph Proust)

A given compound always contains exactly the
same proportion of elements by mass.

Copper carbonate is always 5.3 parts Cu to 4 parts
O to 1 part C (by mass).
Other Fundamental Chemical Laws
Law of Multiple Proportions (by John Dalton)






Mass of O that contributes with 1 g of C
----------------------------------------------------------------------------Compound 1
1.33 g
Compound II
2.66 g
When two elements form a series of compounds, the ratios of the
masses of the second element that combine with 1 gram of the
first element can always be reduced to small whole numbers.
The ratio of the masses of oxygen in CO2 and CO will be a small
whole number (“2”).
Dalton’s Atomic Theory (1808)
 Each element is made up of tiny particles
called atoms.
 The atoms of a given element are identical;
the atoms of different elements are
different in some fundamental way or
ways.
Dalton’s Atomic Theory
(continued)
 Chemical compounds are formed when
atoms combine with each other. A given
compound always has the same relative
numbers and types of atoms.
 Chemical reactions involve reorganization
of the atoms - changes in the way they are
bound together. The atoms themselves are
not changed in a chemical reaction.
Figure 2.4: A representation of some of Gay-Lussac's
experimental results on combining gas volumes.
Avogadro’s Hypothesis (1811)
At the same temperature and pressure, equal
volumes of different gases contain the same
number of particles.
• 5 liters of oxygen
• 5 liters of nitrogen
• Same number of particles!
Figure 2.5: A representation of combining
gases at the molecular level. The spheres
represent atoms in the molecules.
Early Experiments to Characterize the
Atom

J. J. Thomson - postulated the existence of
electrons using cathode ray tubes.

Ernest Rutherford - explained the nuclear
atom, containing a dense nucleus with
electrons traveling around the nucleus at a
large distance.
Figure 2.7 A Cathode-Ray Tube
Figure 2.7: A cathode-ray tube. The fastmoving electrons excite the gas in the tube,
causing a glow between the electrodes.
Figure 2.8: Deflection of cathode rays by an
applied electric field.
Figure 2.9: The plum pudding model of the atom.
Figure 2.10: A schematic representation of the
apparatus Millikan used to determine the charge on
the electron.
Figure 2.12: Rutherford's experiment on
-particle bombardment of metal foil.
Figure 2.13: (a) The expected results of the
metal foil experiment if Thomson's model
were correct. (b)Actual results.
Figure 2.14:
A nuclear
atom viewed
in cross
section. Note
that this
drawing is
not to scale.
Atomic Nucleus
Figure 2.15: Two isotopes of sodium. Both have
eleven protons and eleven electrons, but they differ
in the number of neutrons in their nuclei.
Figure 2.16:
The
structural
formula for
methane.
Figure 2.17: Space-filling model of methane. This
type of model shows both the relative sizes of the
atoms in the molecule and their spatial
relationships.
Figure 2.18: Ball-and-stick model of
methane.
Figure 2.19: Sodium metal reacts with chlorine gas
to form solid sodium chloride.
Figure 2.20: Ball-and-stick models of the
ammonium ion and the nitrate ion.
Figure 2.21: The Periodic Table.
Crystals of copper(II) sulfate.
Various chromium compounds dissolved in water.
From left to right; CrCl2, K2Cr2O7, Cr(NO3)3, CrCl3,
K2CrO4.
Figure 2.22: The common cations and anions
Figure 2.23: A flowchart for naming binary
compounds.
Figure 2.24: Overall strategy for naming chemical
compounds.
Figure 2.25: A flowchart for naming acids. An acid
is best considered as one or more H+ ions
attached to an anion.
Room Temperature Ionic Liquids
室溫離子液體
(pp 520)
Pure Appl. Chem., 2000, 72, 2275–2287
RTIL Structures
• Cations
N+ N
R
R: methyl; R’: n-butyl
R`
1-butyl-3-methylimidazolium, BMIM, C4MIM
• Anions
– PF6– BF4– Cl-
1-butyl-3SbF6methylimidazolium
hexafluorophosphate
CF3SO3- (TfO)
N(CF3SO2)2- (NTf2) [BMIM][PF6]
Effect of the nature of anion on physical properties of BMIM salt
----------------------------------------------------------------------------------Anion
m.p.
d
Viscosity
Conductivity
oC
g/cm3
cP (20oC)
S/m
---------------------------------------------------------------------------------BF4-82(g) 1.17
233
0.17
PF6-8
1.36
312
0.14
Cl65
1.10
solid
solid
CF3COO~-40(g) 1.21
73
0.32
CF3SO316
1.29
90
0.37
(CF3SO2)N- -4
1.43
52
0.39
C3F7COO~-40(g) 1.33
182
0.10
C4F9SO320
1.47
373
0.045
---------------------------------------------------------------------------------(g) Glass transition
P.S. viscosity of water 1 cP.
What is a Room Temperature Ionic Liquid?
(Room Temperature Molten Salt)
• Liquid salt consisting of at least one organic
component (cation or anion)
• Room temperature ionic liquid (RTIL) with melting
point is below room temperature
• Properties:
– Negligible vapor pressure
– High thermal stability (~250-400°C)
– High viscosity
– Hydrophobic or hydrophilic
– Dissolve many organic, organometallic, and
inorganic compounds
RTILs are regarding as “Green solvents”