In the early 1800s, who discovered that each chemical element is made up of a unique type of atom and that atoms differ by their mass?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. John Dalton.
In the early 1800s, John Dalton discovered that each chemical element is made up of a unique type of atom and that atoms differ by their mass. This discovery is part of his atomic theory, which laid the foundation for modern chemistry.