THE HISTORY OF THE ATOMIC THEORYBY Dhruv Rana, Miguel Rivas,

Cristian Tapia

More than 2000 years agoWere from Greece Aristole believed in four elements: Earth, Water, Wind, Fire Democritus thought that matter was composed of small particles called “atoms” They both used observation and inference to explain the existence of the world

Aristole & Democritus

Alchemists

Discovered by European scientists 800 to 900 years ago Their work contributed to what now is

modern chemistry They attempted to turn all objects

possible into gold but failed to do so

John Dalton

During 1808 in England Explained why tiny particles named

atoms could not be divided Thought each element was composed of

its own kind of atom and developed the atom theroy with this scientific research.

J.J. Thompson

During 1897 in England Thompson discovered that the smaller

particles of an atom that were negatively charged electrons

Thompson couldn’t find the positive charge in a atom but knew that it was neutrally charged.

Ernest Rutherford

During 1911 in England He was conducting an experiment to

isolate the positive particles in an atom His conclusion was that an atom was

mostly empty space but had a dense central core

He didn’t know how to arrange positive and negative particle of an atom

Niels Bohr

In 1913, in England He proposed that electrons traveled in

fixed patterns around the nucleus. Scientist still use Bohr’s model today that

show how many number of electrons are in a atom.

He conducted an experiment to show why electron did not get stuck into the nucleus.

ELECTRON CLOUD MODELTHE ELECTRON TRAVELS AROUND THE NUCLEUS IN ROUND ORBIT. SCIENTIST CANNOT PREDICT WHERE THE ELECTRONS WILL BE IN ANY GIVEN TIME.