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Discovery of Proton

Chemistry Formulas

About Discovery of Proton

We know that an atom is electrically neutral, if it contains negatively charged electrons it must also contain some positively charged particles. This was confirmed by Goldstein in his discharge tube experiment with perforated cathode. On passing high voltage between the electrodes of a discharge tube it was found that some rays were coming from the side of the anode which passed through the holes in the cathode. These anode rays (canal rays) consisted of positively charged particles formed by ionization of gas molecules by the cathode rays. The charge to mass ratio (e/m value) of positively charge particles was found to be maximum when the discharge tube was filled with hydrogen gas as hydrogen is the lightest element. e/m varies with the nature of gas taken in the discharge tube. The positive particles are positive residues of the gas left when the gas is ionized.

Production of anode rays in Discovery of Proton

Origin of anode or positive rays:

In the discharge tube the atoms of gas lose negatively charged electrons.  These atoms, thus, acquire a positive charge.  The positively charged particle produced from hydrogen gas was called the proton.

discovery of proton

Properties of Anode rays

  1. They travel in straight lines.  However, their speed is much less than that of the cathode rays.
  2. They are made up of material particles.
  3. They are positively charged, as indicated by the direction of deflection of these rays in the electric and magnetic fields.  That is why they are called ‘positive rays.’
  4. The nature of anode rays depends on the gas taken in the discharge tube.
  5. For different gases taken in discharge tube the charge to mass ratio (e/m) of the positive particles constituting the positive rays is different. 
  6. When hydrogen gas is taken in the discharge tube, discharge to mass ratio (e/m) obtained for anode rays is found to be maximum. i.e., e/m = 9.58 x 104 c/g.

Discovery of Proton brief discussion

  1. Discovery: It was discovered by Goldstein through perforated cathode rays experiment which showed the presence of anode or canal rays.
  2. Charge: It carries unit positive charge i.e. 1.602 x 10-19 coulombs or 4.803x10-10 esu.
  3. Mass: It was found to be 1.672x10-24 g or 1.672 x 10-27 kg.  This mass is 1837 times heavier than an electron.
  4. Specific charge (e/m): It is 9.58 x 104 coulomb/gm (The value of e/m was maximum four hydrogen gas when taken inside the discharge tube. 
  5. Mass of 1 mole of proton is nearly 1.007 mg.
  6. Charge on 1 mole of proton is 96500 coulombs or 1 faraday
  7. The volume of a proton is approximately 1.5x10-38 cm3.
  8. Symbol: +1p0 or 1H1 
  9. Location:  lies inside the nucleus.

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