How did the development of the earliest idea about atoms differ from later work of scientists ?

Ideas about atoms have changed over time.

The development of the earliest idea about atoms differ from later work of scientists because it was based on the thoughts of an early philosopher.

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.