Question

What are the assumptions in Dalton's atomic theory?

Answer 1

He assumed that atoms are indivisible, which has since been proven false.

Explanation:

He states that

1. Everything is made of indivisible atoms.
2. Atoms within an element are unique.
3. Compounds are made of two or more different elements / kinds of atom.
4. Chemical reactions are rearrangements of atoms.

Two centuries later we know that these are not perfect rules, they have exceptions. However, his theory was a theory, rather than widely accepted facts.

This is because many of his ideas about gasses were proven incorrect, and at the time (the early 1800s) it was impossible to see atoms as they are too small.