Discovery of Proton
As we know electron is negatively (-vely) charged particle but atom is
electrically neutral so there should be some particles which have
positive (+ve) charge to neutralize negative (-ve) charge electron.
In 1886, a German scientist E.Goldstein established the presence of
+vely charged particles. These positively charged rays travel from anode
to cathode so called as anode rays or positive rays.
Why anode rays are called as canal rays?
Anode rays passes through canals or perforation in cathode so called as
canal rays.
Properties of Anode Rays
1. Anode rays always travel in straight line.
2. Anode rays rotate light wheel placed in their path that proves anode
rays are made from particles having mass.Which produces mechanical
action.
3. On applying electric field in the path of anode rays, anode rays
turn towards -vely charged plate that proves that anode rays are made up
from positively charged particles.
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Production of Anode Rays |
Determination of charge to mass ratio of proton (e/m)
On the basis of many experiments performed for anode rays, scientist
Wein concluded that charge to mass ratio of proton changes with change
in nature of gases present in discharge tube. This value (e/m) is
maximum for hydrogen gas = 9.58x10
4 coulomb per gram. "Positively charged particle of hydrogen is fundamental particle of matter that is called proton."
Charge on proton
Charge on proton is equal to charge on electron but is of opposite nature.
Charge on proton = 1.602x10
-19 coulomb.
Mass of the proton
For hydrogen gas,
e/m = 9.58x10
4 coulomb per gram
charge of electron = 1.602x10
-19 coulomb
so,
m = (e)/(e/m) = (1.602x10
-19)/(9.58x10
4)
also,
m = 1.67x10
-24 gram
m = 1.67x10
-27 kg
so,
mass of proton is 1837 times more than mass of electron and is equal to mass of an hydrogen atom.
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