John Dalton's atom was a massive, indivisible ball. For him, matter was formed by particles that could not be divided, called atoms.
His work was based on Proust and Lavoisier's Ponder Laws. Dalton used circles of the same diameter with inscriptions to represent the atoms of different chemical elements.
Thus, he established the following postulates:
I) All substances are made up of tiny particles, called atoms, that cannot be created or destroyed. In substances they are united by forces of mutual attraction.
II) Each substance is made up of a single type of atom. Simple substance or elements are formed of "simple atoms" which are indivisible. Compound substances are formed by "compound atoms" capable of decomposing during chemical reactions into "single atoms".
III) All atoms of the same substance are identical in form, size, mass and other properties; Atoms of different substances have different shape, size, mass and properties. The mass of a "compound atom" is equal to the sum of the masses of all the "single atoms" components.
IV) "Compound atoms" are made up of a small number of "single atoms".