The Atomic Model
How was the atom discovered?
John Dalton 1803
Time's 1803 New Man of the Year: John Dalton
It isn't everyday that one gets to witness scientific advances. Well, this year we did, all thanks to John Dalton and his new scientific discovery. Dalton is an English meteorologist, physicist, and chemist born in 1766, with renown work in colorblindness and now chemistry. He proposes that there is something fundamental that make up all matter in the universe, including us humans. Dalton proposes that "atoms" make up elements and are unique within their element. Read TIme's exclusive interview with Dalton to find out how he discovered these atoms and what it means to us.
Interview Excerpt
Times: Hello Mr. Dalton. You're now known for your work in the natural sciences. How did you get interested in it in the first place?
Dalton: My interest first sparked when I was introduced to meteorology. I wanted to learn more about the weather and the world around us, and liked to gather and record data about the weather. I started to record data everyday. Rather than satisfy my curiosity, it fueled it even more.
T: How so?
D: It made me wonder what the atmosphere is really made up of. For an example, my observations led me to conclude that water actually evaporates into the air - but as an independent gas. But how is this possible? I thought to myself. Can water really mix with the air? Why can't solids mix like that? So you see, I reasoned that if water and air were made up of individual particles, then they would be able to mix together when their particles mingled together. While experimenting with this idea, I came up with another conclusion: that different gases must be made out of differently sized particles.
Dalton: My interest first sparked when I was introduced to meteorology. I wanted to learn more about the weather and the world around us, and liked to gather and record data about the weather. I started to record data everyday. Rather than satisfy my curiosity, it fueled it even more.
T: How so?
D: It made me wonder what the atmosphere is really made up of. For an example, my observations led me to conclude that water actually evaporates into the air - but as an independent gas. But how is this possible? I thought to myself. Can water really mix with the air? Why can't solids mix like that? So you see, I reasoned that if water and air were made up of individual particles, then they would be able to mix together when their particles mingled together. While experimenting with this idea, I came up with another conclusion: that different gases must be made out of differently sized particles.
Dalton's Atomic Model | T: Okay, can we go back to the idea of the individual particles making up a substance? What does this mean?
D: Well, atoms, which is what I call these particles, are what make up matter. Each element is made up of unique atoms - or else the elements would be the same. Some atoms are bigger than others. In any case, atoms are indivisible because they are the smallest unit of matter. You just can't get any smaller than that. In addition to not being able to be subdivided, they can't be destroyed or created. Furthermore, when you make mixtures with elements, you are really mixing the atoms. However, these atoms don't just mix together randomly - they have a specific ratio - which I believe is 1:1. Since you can't create or destroy atoms, to make new substances out of old mixtures, the atoms rearrange themselves, and can be combined or separated. |
A Recap of major points in Dalton's Atomic Theory:
1. Elements are made up of small particles (atoms).
2. Atoms within each element are exactly the same.
3. Atoms can't be subdivided, created, or destroyed
4. Chemical compounds are formed when atoms of different elements combine in specific ratios.
5. Atoms can be combined, separated, or rearranged in chemical reactions.
Dalton also thought that the ratio between atoms of different chemicals in all mixtures was 1:1, which is false.
Read more about it here: http://en.wikipedia.org/wiki/John_Dalton#Five_main_points_of_Dalton.27s_atomic_theory