Subatomic Particles - Protons

Chemistry

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Discovery of proton by Goldstein

In 1886, E. Goldstein carried out discharge tube experiments and discovered new radiations and called them canal rays. These rays were made up of positively charged particles and led to the discovery of proton.

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Canal Rays

A canal ray (also positive ray or anode ray) is a beam of positive ions that is created by certain types of gas dicharge tubes.

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Define proton and explain its properties

A proton is a subatomic particle , symbol p or p+, with a positive electric charge of +1 and mass slightly less than that of a neutron present in nucleus of every atom. The number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number (represented by the symbol Z).
properties :
ParticleChargeMass (g)
Proton+11.6727 x 10-24

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Postulates of discovery of protons

The actual mass of proton is 1.672 gram.Proton has mass of 1.00727 atomic mass unit.
Since proton was the lightest positive particle found in atomic beams, found in the discharge tube , it was thought to be present in all other atoms.

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Properties of anode rays

Some of the characteristic properties of anode rays are:

  1. Anode rays consist of material particles.
  2. Anode rays are deflected by electric field towards negatively charged plate. This indicates that they are positively charged.
  3. The charge to mass ratio of the particles in the anode rays was determined by W. Wien by using Thomsons technique. Charge to mass ratio of the particles in the anode rays depends upon nature of the gas taken in the discharged tube.
  4. They travel in straight line.

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Properties of Protons

Electrical discharge carried out in modified cathode ray tube led to the discovery of particles carrying positive charge, also known as 'Canal Rays'. The smallest and lightest positive ion obtained from Hydrogen was called 'proton'. It was first characterized in 1919. Results of these experiments shed some light on physical
properties of protons which are summarized below:
1. Behavior of these particles in magnetic and electric field is opposite to that observed for electron or cathode rays. Hence, they carry a positive charge as opposed to negative charge on electrons.
2. The charge to mass ratio is lower than that of electrons. 

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Important Questions

Which postulate of Dalton's atomic theory is the result of the law of conservation of mass?

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What are canal rays?

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(i) Calculate the number of electrons which will together weighs one gram. 
(ii) Calculate the mass and charge of one mole of electrons.

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Which of the following statements is not correct about the characteristics of cathode rays?

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The increasing order for the values of (charge/mass) for electron (), proton (), neutron () and alpha particle () is:

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Fill in the blanks in the following statements:
(a) The number of protons in the nucleus of an atom is called its ______.
(b) The total number of protons and neutrons in the nucleus of an atom is called ______.
(c) An atom has atomic mass number 23 and atomic number 11. The atom has ______ electrons.
(d) An atom of an element has 11 protons, 11 electrons and 12 neutrons. The atomic mass of the atom is ___________.
(e) If the nucleus of an atom has atomic number 17 , mass number 37 and there are 17 electrons outside the nucleus, the number of neutrons in it is ______.
(f) Almost all the mass of an atom is concentrated in a small region of space called the ______.
(g) Cathode rays are a beam of fast moving ______.
(h) The anode rays obtained from hydrogen gas consist of particles called ______.
(i) The maximum number of electrons that can be accommodated in L shell are ______.
(j) The maximum number of electrons that can go into the M shell is ______.
(k) The subatomic particle not present in a hydrogen atom is ______.
(l) The electron has ______ charge, the proton has ______ charge, and the neutron has ______ charge.

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On the basis of Thomson's model of an atom, explain how the atom is neutral as a whole?

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Which of the following is not a postulate of Dalton's atomic theory?

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Which of the following statements about the electron is incorrect? 

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State the various postulates of Dalton's atomic theory of matter.

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