-
Dalton's atomic theory suggested that atoms are indivisible.
-
Atoms can not be divided further.
-
However, later it was found that atoms contained even smaller particles like electrons and protons.
- Different scientists proposed different models of an atom to explain the structure of an atom.
CHARGED PARTICLES OF MATTER
-
Before the discovery of any model of an atom
-
E.Goldstein
discovered the presence of a new radiation.
-
Electricity was passed through the discharge tube at high voltage through a gas at low pressure taken in a tube.
-
These
rays were positively charged
raditions called
canal rays
.
- It was only because of these rays that charged subatomic particles (particles of an atom) were discovered .
The sub-particles discovered were: -
- Protons (denoted by 'p+')
- Electrons (denoted by ‘e-’)
|
Protons |
Electrons |
|
Protons are positively charged particles. |
Electrons are negatively charged particles. |
|
As estimated by the scientists, a proton is about 2000 times heavier than an electron and weighed about 1 atomic mass unit |
Mass of an electron was very less as compared to a proton. |
|
Charge on a proton was +1 |
Charge on an electron was -1 |
|
It is denoted by " p+ " |
It is denoted by " e- " |