 Name : Vera Gunadi
 Class : VIII A ( 8A )
 Tugas Fisika
DEVELOPMENT OF ATOMIC THEORIES
Perkembangan teori atom
Development of Atomic Theories have some theories , the theories is :
1. Dalton ‘ s Atomic Theories
Teori John Dalton
Recently in the begeining of 19 – th century , a high school teacher in
Manchester , England . The name is John Dalton ( 1766 – 1844 ) Make new
concept about an Atoms .
The an Experiment of John Dalton is this , John Dalton observed two
compounds , those are Carbon monoxide , and Carbon Dioxide . In Carbon
Monoxide , the mass ratio of Carbon , and oxygen is 3 : 4 , while in in carbon
dioxide the mass ratio is 3 : 8 . Thus , the Ratio of Oxygen mass in Carbon
Monoxide , and that in Carbon dioxide 4 : 8 or 1 :2 .
In 1803 years , John Dalton Make a book The T ittle is “ A new system of
chemical phsilosophy “ , and can be explained as follows :
A . Every object or matter consist of smallest particles called atom
B . Atoms are smallest particles of an element which cannot be divided
anymore to be other smaller or simpler particles .
C . atoms are shaped of a dense sphere .
D . Atoms cannot be created or destroyed .
E . Atoms of an element have the same properties , and dimension or size , but
they are different to atoms of another elements .
F . Atoms can combine to form a molecule .
G . A compound is a combination of atoms that consist of atoms of different
kind of elements with the ratio of which is whole , and simple .
The Dalton ‘ s atomic theory is good . In explaining Lavoisier ‘ s law or the law
of mass conservation , and the fixed proportion law (( Proust ‘ s law ) .
2. Thomson ‘ Atomic theory
Teori atom Thomson
In 1898 years , an English physicist Sir Joseph Thomson ( 1856 – 1940
) , succeeded in finding one particle of atom constituents , that is Electron .
It is a Particle of atom constitutes which , is negatively charged . Based on
the Thomson ‘ s discovery , then Dalton ‘ s atomic theory stating that atoms
are the smallest particles of an element is failed .
After Succending , to have found electrons , Thomson proposed an atomic ,
theory , that is atom is a positively charged sphere which at all of the parts the
electrons are evenly spread . According to Thomson , the spreading pattern of
electrons is similar to the plum pudding on a theory . Thomson also explained that
an atom is entirely neutral . I6t is because the number of positive charges in an
atom is equal to the number of its negative charges .
3. Ruthrford ‘ s Atomic Theory
Teori Atom Rutherford
In 1910 , Ernest Rutherford , hans Geiger , and ernest Marsden carried out
an experiment of alpha ( CX ) . Particles scattering . From their experiments ,
Rutherford proposed an atomic theory containing the following opinions . there
are :
a. An atom consist of atomic nucleus which is positively charged , and
electrons which are negatively charged revolving or orbiting the nucleus
.
b. The atomic nucleus is proton , and the number of protons in the nucleus
is equal to that of electrons revolving the nucleus .
4. Bohr ‘ s Atomic Theory
Teori Atom Bohr
Rutherford ‘ satomic theory is opposite to Maxwell ‘ s theory , that is if an
electron in an atom moves orbiting the nucleus , eventually the electron will be
attracted to the nucleus , and finally fallen to thee atomicnucleus because it
moves while radiating an amount of energy .
To have overcame the weakness of Rutherford ‘ d atomic theory , then a
Dannish physicist Niel Bohr ( 1885 – 1962 ) pproposed an anatomic theory , that is
as follows , there are :
a. Electrons move to orbit the nucleus at a certain path , and don ‘ t radiate an
amount of energy .
b. The certain paths are called atomic shells .
c. In the atomic shells , electrons are at a certain energy level ( stationary
state ) .
d. Energy will be radiated when electrons displace from one shell to another .
5. Modern Atomic Theory
Teori Atom Modern
According to the development of science , and technology , then the
theories about atom also develops . Hence , in the next development Bohr ‘
s atomic theory also has several weakness . The discovery of electrons ,
protons , and neutrons bases the birth of the modern atomic theory .
However , not all of the prior atomic theories are incorrect , it may be
needed a given repairing , and competing .