Atomic struture and radioactivity

Discovery of nucleusDiscovery of nucleus&&

Theory of atomic Theory of atomic disintegrationdisintegration

ERNEST RUTHERFORD: FATHER OF NUCLEAR SCIENCE• Work-• He worked as a research student

under J.J.Thomson.• In 1898 he reported existance of

alpha particle in uranium radiation.

• In collaboration with Soddy developed theory of atomic disintegration.

• Steered other future noble prize winner towards their achievements e.g. Chadwick etc.

1871-1937

•Radioactive decay unit Rutherford(rd) was given on the name of Rutherford.•Rutherfordium(Rf,Z-104) was named on the name of Rutherford.•Many countries issued stamps and currency with his photo

CURRENCY ISSUED BY CURRENCY ISSUED BY NEWZEALANDNEWZEALAND

STAMP ISSUED BY DIFFERENT STAMP ISSUED BY DIFFERENT COUNTRIESCOUNTRIES

Rutherford’s Apparatus

Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 120

beam of alpha particles

radioactive substance

fluorescent screencircular - ZnS coated

gold foil

What he expected…

California WEB

What he got…richochetingalpha particles

• Hit moth driving car – no change in car direction

• Hit deer – car changes direction

Alpha particle

Large angle of deflection, must have hit massive object!

moth

deer

Gold Atom

DRAWBACKS OF RUTHERFORD MODEL..

• Stability of nucleus• Well defined lines of spectrum of

different frequency• The theory was unable to explaine the

distribution of electron in the atom

WHAT HOLDS A NUCLEUS WHAT HOLDS A NUCLEUS TOGETHERTOGETHER..

•

A strong nuclear force

BINDING ENERGY

THEORY OF DISINTEGRATION

• nuclei of Radioactive element are unstable.

• Disintegration is spontaneous.• During disintegration elements physical and chemical property changes.

• During disintegration alpha or beta particles are emmited.

•

ALPHA DECAY

BETA DECAY

ELECTRON CAPTUREELECTRON CAPTURE

3 reasons why we should stop using nuclear energy• Nuclear weapon proliferation

• Nuclear waste and energy• Accident and disasters