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Atomic Theory

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Title: Atomic Theory


1
Atomic Theory
2
Throughout history man has attempted to explain
the nature of matter.
3
Democritus, an early Greek, proposed that matter
was composed of tiny indivisible particles called
atoms, meaning indivisible.
4
It was not until 1807 that the atomic theory was
thoroughly revised by John Dalton.
5
Daltons theory stated
  • All matter is made up of tiny particles called
    atoms that cannot be split into smaller particles
    (wrong).
  • Atoms cannot be created or destroyed
  • All atoms of the same element have the same
    properties and atoms of different elements have
    different properties.
  • Atoms of different elements can combine to form
    new substances.

6
His ideas marked the beginning of the modern
atomic theory.
7
The work of later scientists such as JJ Thomson,
Lord Rutherford and Neils Bohr established a
workable model of the atom.
Thomson
Rutherford
Bohr
8
Dalton stated that the atom is a hard, dense
sphere.
9
Thomson in 1903 stated that the atom is a mass of
positive charge and contained negative electrons.
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10
Rutherfords Model in 1911 described the atom as
having a dense nucleus surrounded by electrons.
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11
Bohr developed a model in 1913 that had a dense
nucleus and electrons that move in fixed orbits
(shells) around the nucleus in a cloud of
activity

12
http//micro.magnet.fsu.edu/electromag/java/ruther
ford/http//particleadventure.org
13
James Chadwick (1885 - 1962) developed a new
model of the atom in 1932. Similar in many ways
to other models, his showed the nucleus made up
of particles called neutrons.
14
10,000,000 atoms placed side by side would
measure only 1 cm.
15
The particles inside atoms are called subatomic
particles. In the middle of every atom is its
nucleus.
16
The nucleus is made of the proton and neutron. A
third type of subatomic particle spins around the
nucleus, it is called the electron.
17
Proton
Neutron
Electron
18
Proton
Neutron
Electron
19
Proton
Neutron
Electron
20
Proton
Neutron
Electron
21
Proton
Neutron
Electron
22
Proton
Neutron
Electron
23
Proton
Neutron
Electron
24
Proton
Neutron
Electron
25
Proton
Neutron
Electron
26
Proton
Neutron
Electron
27
Proton
Neutron
Electron
28
Proton
Neutron
Electron
29
Proton
Neutron
Electron
30
Proton
Neutron
Electron
31
Proton
Neutron
Electron
32
Proton
Neutron
Electron
33
Proton
Neutron
Electron
34
Proton
Neutron
Electron
35
Proton
Neutron
Electron
36
Proton
Neutron
Electron
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Proton
Neutron
Electron
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Proton
Neutron
Electron
39
Proton
Neutron
Electron
40
Proton
Neutron
Electron
41
Proton
Neutron
Electron
42
Proton
Neutron
Electron
43
Proton
Neutron
Electron
44
Proton
Neutron
Electron
45
The electron is by far the smallest of these
subatomic particles. Their mass is only 1/1840th
the mass of a proton.
46
Even though protons are much larger than
electrons, they both have the same amount of
electrical charge.
47
Protons have a positive charge ().Electrons
have a negative charge (-).Neutrons have no
charge (0).
48
Particles with opposite electrical charges are
attracted to each other, in the same way that
magnets with opposite poles stick together.
49
Got a problem, ask a chemist, they have solutions.
50
A small piece of sodium which lived in a test
tube fell in love with a bunsen burner. Oh
bunsen, my flame, I melt whenever I see you the
sodium said.Its just a phase youre going
through replied the Bunsen burner.
51
Particles with the same electrical charges repel
each other, in the same way that magnets with the
same poles push apart.
52
Atoms have the same number of protons as
electrons, so their electrical charges cancel
each other out, and are called neutral.
53
Atoms are normally neutral and have no overall
electrical charge. This is not the case with
ions.
54
Ions are charged atoms that have gained or lost
electrons. When atoms are unbalanced, it causes
them to combine or react.
55
Electrons travel in shells. The first shell
contains 2 electrons, the second 8, third 8, the
fourth 18 and so on.
N
56
If an atom gains an electron it becomes
negatively charged. If an atom loses an electron
it becomes positively charged.
57
The number of neutrons of an atom can vary. The
different atoms caused by varying numbers of
neutrons is called an isotope.
58
Different electrons can contain different amounts
of energy.
59
The farther an electron is from the nucleus, the
more energy it contains.
60
The number of protons an atom has determines the
type of element. If the number of protons
change, the type of atom changes.
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