Show Menu
Cheatography
  1. Home >
  2. Education >

structure of atoms Cheat Sheet (DRAFT) by

This cheat sheet would be found by the readers to be very beneficial. all the information has been provided in simplified yet concise manner. This is not the complete work but surely will soon be.

This is a draft cheat sheet. It is a work in progress and is not finished yet.

DISOVERY OF SUB ATOMIC PARTICLES

DISCOVERY OF ELECTRON

Michael Faraday in 1850s used Cathode Ray discharge tube to study electrical discharge
Between electrodes voltage applied -10000V
Pressure reduced- 10-4atm/(0.01mm)
Phosph­ore­scent Material like zinc sulphide used on glass wall behind anode to observe the emitted rays from cathode
when a perforated anode is used glow between electrode disappears but current continues to flow a faint greenish glow is observed on the glass wall due to the rays emitted by cathode which pass through the holes of anode.
these rays are called Cathode rays due to their origin.

Charac­ter­istics of Cathode Rays

they travel in a straight line
they consist of material particles as they show mechanical effects
they consist of electrons
they show heating effect
they produce x rays
they cause ionization of gas through which they pass
they affect the photog­raphic plates
they posses penetr­ating effect
These charac­ter­istics were concluded as a result of various experi­ments performed byJJ Thomso­n(1897) and others.

CHARGE AND MASS OF ELECTRON

CHARGE TO MASS RATIO
**CHARGE ON THE ELECTRON: Milikan's Oil Drop Exp.
MASS OF THE ELECTRON
By measuring the amount of deflec­tions the electric field strength or magnetic field strength Thomson calculated the value of the ratio
Mass can be calculated from the values of e/m
e
and e
e/m
e
=1.758­820x1011Ckg-1
Using an atomiser small drops of oil are allowed to fall between 2 electr­ically charged plates
m
e
=e/e/m
e
=1.6022x 10-19C/1.75­8820X 1011C kg-1
 
Milikan observed the rate of their fall as to measure mass of these droplets
m
e
=9.1094x 10-31kg
 
Using x-ray he ionised the gas inside the chamber
the mass 9.11x 10-28 g is nearly 1/1837th of the hydrogen atom
 
because of the collisions with gaseous ions their droplets now had electrical charge on them.
 
By observing the effects of electrical field strength on the motion of oil droplets milk and concluded that the magnitude of electrical charge q, on the droplets is always an integral multiple of the electrical charge, e.
 
I.e. q=ne where n= integer sub as 1,2,3...
 
the value of this charge is -1.6022x10-19or 4.8x10-10esu
 
esu is the smallest measurable quantity of charge and is called one unit.