Dalton theorized that the atom was simply a solid space

Five main points of Dalton's Atomic Theory 

Elements are made of tiny particles called atoms 
All atoms of a given element are identical 
The atoms of a given element are different from those of any other element 
Atoms of one element can combine with atoms of other elements to form compounds. A given compound always has the same relative numbers of types of atoms. 
Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process. A chemical reaction simply changes the way atoms are grouped together. 
So, number two, indivisible.

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