He designed an experiment using an extremely thin sheet of gold foil and the screen coated with zinc sulfide. Taken by New Zealander Earnest Rutherford in 1909. And while a singleĮlectron's motion is random the overall distribution of them is not. Even today Thompson's model of the atom continues to be called The positive matrix being the cake, and the electrons the random floating bits of fruit within it. And the very English Thompson visualized this model as a familiar English dessert. The next question was, 'How were they arranged in the atom.' Thompson knew that the atom overall had a neutral charge so he immagined that the negatively charged electrons must be distributed randomly in a positively charged matrix. So even though we didn't understand what shapes they took, we knew that they were both negative and positive components to matter. He concluded that the cathode rays weren't rays or waves at all, but were in fact very light, very small negatively charged particles.

Times lighter than hydrogen, the smallest bit of The cathode rays generated, how much they could be bentīy magnets and other things, he was able to estimate J.J.Thompson took the discharge tube research further. I mean scientists still hadn't figured out what was responsibleįor the negative charge in the rays either. Goldstein didn't fully understand what he'd discovered here. In the opposite direction, which meant that there must also must be a positive charge in matter. Physicist Eugen Goldstein found that the tubes also emitted light from the positive electrode, basically a ray heading Because this light was originally produced by a negative electrode or a cathode it was called a cathode ray and it had a negative charge. Basically gas filled tubes with electrodes at each end, which emit light when an electric current passes through them. In the 1870's scientistsīegan probing what stuff was made of using discharge tubes. The next logical question was, 'Why? Why do they behave the way they do?' This led to the investigation Thanks to these and other great minds by the 1800's we had a better grip on the general behavior of atoms. The English teacher James Dalton who determined that elements exist as discrete Matter changes in shape or form, its mass stays the same. Of Conservation of Mass which states that even if I've already told you, for instance about the French chemist Antoine Lavoisier who proposed the Law In atomic theory didn't come along for nearly 2,300 years. Once Leucippus and Democritus came up with the general idea of atoms it'd be pretty easy for someone else to take that little indivisible ball and run with it. But before we do I wanted to set aside some time to explain how we know what we know about the atom today, and how we know that we're not quite done figuring it out. We've been talking a lot about the fine details ofĬhemistry in recent weeks and we're gonna keep doing that as we move on to nuclear chemistry, and then to the basics But, as has been the case in all science, each scientist built on what As time went on many more were the result of rigorous experimentation. Some models like that of Leucippus were just blind guesses. Hundreds if not thousands of different insights. Theory as we know it today is the product of Then this makes a certain amount of sense if you don't happen to haveĪccess to electron microscopes or cathode ray tubes or the work of generations Clay atoms were softer and attached by ball socket joints that So they thought that iron atoms were hard and stuck together with hooks. Properties of each substance the forms of the atom. Thought that iron was made up of iron particles and clay was made up of clay particles and cheese was made up of cheese particles. The name a tomos, which means uncuttable or indivisible. In half enough times, eventually you'll reach a particle that can't be cut anymore. Special they just thought that if you cut something No one knows how theyĭeveloped this concept but they didn't think the particles were particularly That's when Greek philosopher Leucippus and his pupil Democritus first came up with the idea that matter isĬomposed of tiny particles. And like way more than they thought they knew 2,500 years ago.

Know more about atomic theory then the scientists did If you understand enoughĪbout atoms to visualize any of those things then you How do you picture an atom in your mind? Like this, or like this,

Atom theory