Final answer:
The history of atomic theory begins with John Dalton's modern atomic theory, which stated that all elements are composed of atoms and can combine in fixed ratios to form compounds. However, Dalton's theory was later refined and modified as new insights into atoms were gained through experiments and observations.
Step-by-step explanation:
The history of atomic theory can be traced back to the modern atomic theory proposed by English chemist John Dalton in 1803. Dalton's theory stated that all elements are composed of atoms, which are the smallest part of an element that maintains the identity of that element. He also proposed that atoms of different elements can combine in fixed, small, whole-number ratios to form compounds. However, over time, Dalton's ideas were refined and modified as new experiments and observations provided more insights into the nature of atoms and their behavior.