The atomic theory has changed much since John Dalton's time. In the late seventeen hundreds John Dalton first discovered that elements combine in specific proportions because they are made of individual atoms. For example, hydrogen and chlorine always combine in a specific proportion to create hydrochloric acid. Dalton thought that atoms were small particles, like a small marble. Dalton's atomic theory consisted of three parts. They were: *All substances are made of atoms. Atoms are …showed first 75 words of 527 total…

…showed last 75 words of 527 total…seemed too simple to scientists though. Scientists now think that the definite path of an atom cannot be predicted. They travel around in a predicted region because they do not move around in straight paths. These regions where they are likely to be found are called electron clouds. These clouds are like the paths of Bohr's model. Scientists still aren't sure about the definite structure of atoms , but they think that they are very close