-
8/18/2019 004-Characterize the Atoms
1/12
1
Characterize the Atoms
On the basis of the work of Dalton, Gay-
Lussac, Avogadro, and others, chemistry was beginning to
make sense. The concept of
atoms was clearly a good idea. (p44, 1)
Scientists began to wonder about the natureof the atom.
What is an atom made of, and how do the
atoms of the various elements differ?
-
8/18/2019 004-Characterize the Atoms
2/12
2
Cathode-Ray Tube Experiment
Cathode-ray tube
J. J. Thomson
-
8/18/2019 004-Characterize the Atoms
3/12
3
Deflection of Cathode Rays
pp44-45
-
8/18/2019 004-Characterize the Atoms
4/124
Results from Cathode-Ray Tube Exp.
p44, 2-5
Postulated the existence of electrons using
cathode-ray tubes.
Determined the charge-to-mass ratio of anelectron. (
e
m= 1.76 10
8C/g )
The atom must also contain positive particles
that balance exactly the negative charge
carried by particles that we now call electrons.
-
8/18/2019 004-Characterize the Atoms
5/12 5
Plum Pudding Model of the Atom
p45, Figure 1.13
-
8/18/2019 004-Characterize the Atoms
6/12 6
Millikan’s Oil-Drop Experiment
p45, Figure 1.14
-
8/18/2019 004-Characterize the Atoms
7/12 7
Millikan’s Oil-Drop Experiment
補充
-
8/18/2019 004-Characterize the Atoms
8/12 8
Mass of an Electron
kg1011.9g10382901.9
C/g10820857.1C10176260.1
C10176260.1
C/g10820857.1
3128
8
19
19
8
m
e
m
e
-
8/18/2019 004-Characterize the Atoms
9/12 9
Results from Oil-Drop Experiment
pp44-45
(Performed experiments involving charged
oil drops.)
Determined the magnitude of the charge on asingle electron.
Calculated the mass of the electron.
-
8/18/2019 004-Characterize the Atoms
10/1210
Rutherford Scattering Experiment
p46, Figure 1.16
Ernest Rutherford
-
8/18/2019 004-Characterize the Atoms
11/1211
Plum Pudding Model of the Atom
p46, Figure 1.17
Expect result (incorrect) Actual result
-
8/18/2019 004-Characterize the Atoms
12/1212
Results from Scattering Experiment
p46, r2
Explained the nuclear atom.
Atom has a dense center of positive charge
called the nucleus. Electrons travel around the nucleus at a
relatively large distance.
