Chapter 2
Atoms and
Elements
2011, NKMB Co., Ltd.
Chemistry, Julia Burdge, 2
st
Ed.
McGraw Hill.
Mr. Truong Minh Chien ;
/>
Modern Evidence for Atoms
IBM's Almaden Research Center in San Jose,
California, April 1990
2
Chemistry, Julia Burdge, 2
nd
e., McGraw Hill.
Tro, Chemistry: A Molecular Approach 3
Scientists First To Image
'Anatomy' Of A Molecule
ScienceDaily (Aug. 29, 2009) —
IBM scientists have been able to
image the “anatomy” -- or chemical
structure, chemical bonds -- inside
a molecule with unprecedented
resolution, using a complex
technique known as noncontact
atomic force microscopy.
4
Scanning Tunneling Microscope
•

•
Since there was no experimental way of proving who
was correct, the best debater was the person assumed
correct, i.e., Aristotle
Chemistry, Julia Burdge, 2
nd
e., McGraw Hill.
7
Scientific Revolution
•
in the late 16
th
century, the scientific approach to
understanding nature became established
•
for the next 150+ years, observations about
nature were made that could not easily be
explained by the infinitely divisible matter
concept
Chemistry, Julia Burdge, 2
nd
e., McGraw Hill.
8
Law of Conservation of Mass
•
in a chemical reaction, matter
is neither created nor
destroyed
•
total mass of the materials

Law of Definite Proportions
•
All samples of a given
compound, regardless of
their source or how they
were prepared, have the
same proportions of their
constituent elements
Joseph Proust
1754-1826
Chemistry, Julia Burdge, 2
nd
e., McGraw Hill.
11
Proportions in Sodium Chloride
54.1
g 39.3
g 7.60
Na of mass
Cl of mass
==
a 100.0 g sample of sodium
chloride contains 39.3 g of sodium
and 60.7 g of chlorine
a 200.0 g sample of sodium
chloride contains 78.6 g of sodium
and 121.4 g of chlorine
54.1
g 78.6
g 21.41

nd
e., McGraw Hill.
Law of Multiple Proportions animat
ion
Tro, Chemistry: A Molecular Approach 13
14
Oxides of Carbon
•
carbon combines with oxygen to form
two different compounds, carbon
monoxide and carbon dioxide
•
carbon monoxide contains 1.33 g of
oxygen for every 1.00 g of carbon
•
carbon dioxide contains 2.67 g of
oxygen for every 1.00 g of carbon
•
since there are twice as many oxygen
atoms per carbon atom in carbon dioxide
than in carbon monoxide, the oxygen
mass ratio should be 2
2
g 1.33
g 2.67
monoxide carbon in carbon of g 1 withcombines that oxygen of mass
dioxide carbon in carbon of g 1 withcombines that oxygen of mass
==
Chemistry, Julia Burdge, 2
nd

Like charges repel

+ repels +

– repels –
•
To be neutral, something
must have no charge or
equal amounts of opposite
charges
Chemistry, Julia Burdge, 2
nd
e., McGraw Hill.