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.
|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 = 9.58×104 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 = 1.602×10-19 coulomb.
Mass of the proton
For hydrogen gas,
e/m = 9.58×104 coulomb per gram
charge of electron = 1.602×10-19 coulomb
m = (e)/(e/m) = (1.602×10-19)/(9.58×104)
m = 1.67×10-24 gram
m = 1.67×10-27 kg
mass of proton is 1837 times more than mass of electron and is equal to mass of an hydrogen atom.
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