Chemistry Atomic Structure and Radioactivity Part-3
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Atomic Structure and Radioactivity Part-3

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Discovery of anode rays/canal rays

`=>` Sir Goldstein a physicist discovered anode rays when he was working on light emitted in discharge tubes (Crookes tubes) and the influence of magnetic field on this radiation.

`=>` He carried out experiment in discharge tube containing perforated cathode. The light radiation produced in discharge tube moved towards cathode and passed through the perforation in the Cathode.

`=>` These rays were called canal rays because they pass through the canals or holes of the Cathode. '

`=>` These rays are also called anode rays since they originate from the anode side.

`=>` Anode rays are positively charged, therefore these were named positive rays by Sir J .J . Thomson.

Properties of Anode Rays

`=>` Travel in a straight line and cast shadow.
`=>` Possess kinetic energy and also have heating effect.
`=>` The anode rays are deflected by the magnetic and electric field and bent in the opposite direction of cathode rays.
`=>` The charge to mass ratio (`e//m`) depends upon the nature of the gas taken in the tube and it is less than e/m of electron. `e/m = 9.579xx10^7 C kg^(-1)`
`=>` The removal of electrons from neutral atoms or molecules of gas give positively charged ions. These positively charged ions move towards perforated cathode and constitute beam of positive rays.
`=>` These rays affect the photographic plate.
`=>` The discharge tube consist of atom of hydrogen gas, on passage of electric current these atom loses negatively charged electrons. In the discharge tube, the atoms of gas lose negatively charged electrons.
`H overset (e^(-))->H^(+) ("Proton")`
Thus these atom acquire a positive charge. The positively charged particle produced from hydrogen gas were called "protons" .

Characteristics of proton

`=>` A proton may be defined as a fundamental particle of atom carrying one unit positive charge of having mass nearly equal to the mass of an atom of hydrogen.

`=>` Proton is a positively charged particle.

`=>` The charge on a proton is equal but opposite to that on an electron.

`=>` The magnitude of charge on a proton is `+ 1 .602 xx 1 0^(-1 9)` coulomb/unit

Discovery of neutron

`=>` The neutrons were discovered by James Chadwick.
`=>` These particles are neutral having charge equals to zero.
`=>` Their mass is approximate same as that of a hydrogen atom. i.e. `1.675 xx 10^(-27) kg`.
`=>` According to Rutherford there were some neutral particles present in the nucleus, this thought came into picture due to difference between an elements atomic number and atomic mass.
`=>` In order to find out the evidence for Rutherford's statement a scientist named "Chadwick" successfully attempted an experiment
to tracking down the mystery about the tightly bounded proton pair i.e neutron .
`=>` He bombarded beryllium with a stream o f a-particle. He observed that penetrating radiations were produced which were not affected by electric & magnetic field.
`=>` These radiations consists of neutral particles, which were called neutron.
`=>` The n uclear reaction can be shown as:

` underset("Beryllium")(text()_4^9 Be) + underset(alpha-"particle")(text()_2^4 He )-> underset("carbon")(text()_6^12 C) + underset("Neutron")(text()_0 n^1)`

Beryllium on bombardment with alpha particles gave carbon atom and a neutron. In this equation the subscript stand for number of protons and the superscript for mass n umber.
It is now clear that the neutron is fundamental constituent of atom and is located in the n ucleus
 
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