5th Period Beginning of Chemistry Blog Response

Main Characters- John Dalton, Michael Faraday, Johannes Hittorf, William Crookes, J.J. Thompson, William Roentgen, Esnst Rutherford, Robert Millikan, A. van den Broek, H.G.J. Moseley, James Chadwick

Vital to the Development-

Dalton- Atomic Theory

Faraday- cathode and anode

Hittorf- Found that when a solid object was placed between the cathode and anode, a shadow was cast on the end of the tube across from the cathode.

Crookes-Developed a better vacuum pump that allowed him to produce cathode-ray tubes with a smaller residual gas pressure.

Thompson-There must be positively chargedparticles which also must carry the mass of theatom. Dalton's model is now incorrect becauseatoms are divisible.

Roentgen- Discovered x-rays while using cathode-ray tubes. Found that x-rays could passthrough solid objects.

Rutherford-Studied absorption of radioactivity.

Millikan- measured the charge on an electron with his oil-drop apparatus

Broek- Suggested that the positive charge on atoms should be compared to their atomic numbers, not their atomic weights.

Moseley-Found that there was a relationship between the frequencies (v) of the x-rays given off by the cathode-ray tube and the atomic number of the metal used to form the anode:

Chadwick- Proved that neutrons, neutral particles in the nucleus that made up approximatelyhalf the mass of an atom, did exist.



What made them different-

All these scientists were very different. Although they were ultimetly studying the same general thing their studies were very specific. However, each study contributed to the bigger picture of learning more about the atom.



Time Period They Lived in Determined Outcome-

Obviously the technology of the time was not even close to advanced as it is in the twenty-first century. During the 1930s things such as parking meters, regular television service, and radio telescopes were being discovered. Therefore this hindered the scientists abilites to discover new things. Which makes their discoveries that much more impressive.



Why is the atomic theory still a theory? New Developments?

Unexplained chemical phenomena was quickly explained by Dalton with his theory. Dalton's theory quickly became the theoretical foundation in chemistry.

It is still a theory because the discovery of nuclear fusion/fission and radioactivity prompted revision of point #2. Isotopes prove that atoms of the same element can actually have small differences due to a different number of neutrons. Also, the existence of ions with varying numbers of electrons also contradicts this point

Modern atomic theory is a little more involved than Dalton's theory but the essence of Dalton's theory remains valid. Today we know that atoms can be destroyed via nuclear reactions but not by chemical reactions. Also, there are different kinds of atoms (differing by their masses) within an element that are known as "isotopes", but isotopes of an element have the same chemical property.

Why does it matter that we understand the structure of the atom?

It matters because atoms are all around us. Therefore, to understand our natural world and the things around us we need to know how an atom works. The basic idea of the atom is atomic structure. If you do not know atomic structure then it is difficult to really study what the atom is.