draw a timeline to show how atomic theory has developed over the past several hundred years.
Answers
I am not going to go into the experimental evidence for Dalton’s model of the atom, it’s good stuff though. Let me just state what Dalton said:
Stuff can be broken into elements (the things listed on the periodic table).Elements are atoms with different masses.Compounds are a combinations of elements. You know, like water, salt or pizza.Thomson played with cathode rays. These are just beams of electrons (but cathode ray sounds cooler). By having the beam interact with electric and magnetic fields, Thomson was able to determine the mass to charge ratio for an electron. So, from that he knew that the electron came from the atom, it had a negative charge and a small mass. Here is the model that he proposed.
Ernest Rutherford said one day “hey, I think I will shoot some stuff at atoms.” I am sure his wife said “oh, Ernie” (she probably called him Ernie) “if it makes you happy to play with your little physics stuff, go ahead. I know how much you like it.” So he did. He shot some alpha particles (which are really just the nucleus of a helium atom) at some really thin gold foil. Here is a diagram of his experiment.
The model proposed by Niels Bohr is the one that you will see in a lot of introductory science texts. There are a lot of good ideas in this model, but it is not the one that agrees with all of the current evidence. The model tries to make a connection between light and atoms.
Suppose you take some light and you let different colors bend different amounts (think rainbow). This way, you could see what colors are present for different light sources. Here are three different light sources.