CLASS XI CHEMISTRY
UNIT 2
STRUCTURE OF ATOM
Topics:-
• Discovery of electron, proton and neutron,
By:- Vijay Kumar Sethi
,Discovery of Electron
• Scientists mainly Faraday performed experiments
using cathode ray discharge tubes.
• A cathode ray tube is made of glass containing two
thin pieces of metal, called electrodes, sealed in it.
• At very low pressure and at very high voltages, a
stream of particles moving in the tube from the
negative electrode (cathode) to the positive electrode
(anode) was observed.
• These were called cathode rays or cathode ray
particles.
,Discovery of Electron
• The flow of a stream of particles from cathode to anode was further
Giving off light
checked by using perforated anode and coating the tube behind anode with after radiation
phosphorescent material zinc sulphide. has hit it
• When these rays, after passing through anode, strike the zinc sulphide coating, a
bright spot is developed on the coating
• These rays themselves are not visible but their behaviour can be observed with
the help of certain kind of materials (fluorescent or phosphorescent) which glow
when hit by them.
• Television picture tubes are cathode ray tubes and television pictures result due
to fluorescence on the television screen coated with certain fluorescent or
phosphorescent materials. Fluorescent materials cease to glow nearl
immediately when the radiation source stops
unlike phosphorescent materials, which
continue to emit light for some time after.
, Characteristics of Cathode Rays
• Travel in straight line.
• Consist of Particles.
• Particles consisting cathode rays are negatively charged
• Cathode rays can ionize gas.
• They can heat objects that they hit
• Charge/mass ratio of the particles is independent of nature of material of electrode and
nature of gas present in Cathode ray tube.
• These particles were named as electron by J.J Thomson
UNIT 2
STRUCTURE OF ATOM
Topics:-
• Discovery of electron, proton and neutron,
By:- Vijay Kumar Sethi
,Discovery of Electron
• Scientists mainly Faraday performed experiments
using cathode ray discharge tubes.
• A cathode ray tube is made of glass containing two
thin pieces of metal, called electrodes, sealed in it.
• At very low pressure and at very high voltages, a
stream of particles moving in the tube from the
negative electrode (cathode) to the positive electrode
(anode) was observed.
• These were called cathode rays or cathode ray
particles.
,Discovery of Electron
• The flow of a stream of particles from cathode to anode was further
Giving off light
checked by using perforated anode and coating the tube behind anode with after radiation
phosphorescent material zinc sulphide. has hit it
• When these rays, after passing through anode, strike the zinc sulphide coating, a
bright spot is developed on the coating
• These rays themselves are not visible but their behaviour can be observed with
the help of certain kind of materials (fluorescent or phosphorescent) which glow
when hit by them.
• Television picture tubes are cathode ray tubes and television pictures result due
to fluorescence on the television screen coated with certain fluorescent or
phosphorescent materials. Fluorescent materials cease to glow nearl
immediately when the radiation source stops
unlike phosphorescent materials, which
continue to emit light for some time after.
, Characteristics of Cathode Rays
• Travel in straight line.
• Consist of Particles.
• Particles consisting cathode rays are negatively charged
• Cathode rays can ionize gas.
• They can heat objects that they hit
• Charge/mass ratio of the particles is independent of nature of material of electrode and
nature of gas present in Cathode ray tube.
• These particles were named as electron by J.J Thomson
