History of the Atomic Theory

Science as we know it today did not

exist several thousand years ago.  

 

Many philosophers speculated that matter was composed of things such as

earth, water, air, and fire. 

It was also commonly accepted that matter could be

endlessly divided into smaller and smaller pieces

democritus

• He was a Greek philosopher (460-370 B.C.) who was the first to propose that 

democritus was the

first to propose that matter was not infinitely divisible.  

He believed matter was made up of

tiny particles called atoms that could not be created, destroyed, or further divided 

who was Aristotle 

• This Greek philosopher (384-322 B.C.) disagreed with Democritus. 

 

Aristotle did not believe that

• empty space could exist. 

Arisotle views went

unchallenged for 2,000 years

who was john dalton

English schoolteacher (1766-1844) whose work marks the beginning of the  development of modern atomic theory.  

 

Dalton revived and revised

Democritus’s ideas based on the results of scientific research.

Results of his research are known as

Dalton’s atomic theory. 

What is daltons atomic theory

Matter is made of extremely small particles called atoms. 

Atoms are indivisible and indestructible. 

Atoms of a given element are identical

in size, mass, and chemical  properties

Atoms of a specific element are different from

those of another element. 

Different atoms combine

in simple whole-number ratios to form 

compounds.  

In a chemical reaction, atoms are

 

separated, combined, or rearranged. 

 

The law of conservation of mass states that

 mass is conserved in any 

process.  

The conservation of mass in chemical reactions is the

result of the rearrangement of atoms during the reaction.