The main people involved with the atom would have to be Democritus, John Dalton, and Lavosier. Democritus states that all matter is composed of tiny indestructiable units called atoms. With Democritus then knowing (or hypothesizing) that everything is made up of tiny atoms leaves room for other scientist then to come up with there own ideas that usually always pertain to Democritus's theory. Then Lavosier found out that the element is the simpliest substance and cannot be broken down any further. He also stated that element react with eachother in the same proportions and therefore called that compounds. All of Lavosiers findings with the careful measurements and use of elements then helped Dalton. Such as Dalton stating that you could distinguish the weight diffrence between diffrent elements. Dalton then states that all matter is composed of atoms going back to what Democritus first states.

I do not really see any diffrences between these scientist. They all seem to work off of whatever the scientist before them has stopped at.

It is called the "atomic theory" because we are still learning new things about the atom and how it works. The theory simply means that its a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena. http://www.thejakartaglobe.com/afp/atom-smasher-scientists-spot-potential-new-discovery-cern/397426 at this website it tells about the latest thing they have done with the atom to help learn about the universe.

The reason we should know about the atom is because it can help us learn about diffrent things such as the universe. It shows us that even the tiniest thing the atom is made up of diffrent parts neutrons, electrons, and protons.