Atom

-Who were the main characters in the development of the atom?
· 1803 - John Dalton
· 1830 - Michael Faraday
· 1869 - Johannes Hittorf
· 1879 - William Crookes
· 1897 - J.J. Thompson
· 1895 - William Conrad Roentgen
· 1899 - Ernst Rutherford
· 1908-1917 - Robert Millikan
· 1913 - A. van den Broek
· 1914 - H. G. J. Moseley
· 1932 - James Chadwick

- Why were they vital to the development of the atom?

· John Dalton – Atomic Theory
· Michael Faraday - Cathode - metal plate connected to the negative end. Anode - metal plate connected to the positive end.
· Johannes 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.
· William Crookes - Developed a better vacuum pump that allowed him to produce cathode-ray tubes with a smaller residual gas pressure.
· J.J. Thompson - Found that cathode rays could be deflected by an electric field, showed that cathode "rays" were actually particles, found the charge to mass ratio of the particles to be approximately 108 Coulomb (C) per gram, same charge to mass ratio regardless of metal used for cathode/anodeor gas used to fill the tube.
· William Conrad Roentgen - Discovered x-rays while using cathode-ray tubes. Found that x-rays could passthrough solid objects.
· Ernst Rutherford - Studied absorption of radioactivity.
· Robert Millikan – Oil-drop experiment.
· A. van den Broek - Suggested that the positive charge on atoms should be compared to their atomic numbers, not their atomic weights.
· H. G. J. Moseley - Studied the frequencies of the x-rays given off by cathode-ray tubes when electrons strike the anode. 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
· James Chadwick - Proved that neutrons, neutral particles in the nucleus that made up approximately half the mass of an atom, did exist.- Think about your lessons in history and discuss how the time period that they lived in determined the outcome of their discovery/ or how it influenced those individuals to be the names that we know today (aka did it matter where they grew up or if they had money?)

· Their money or background didn’t matter, of course it could have changed the way they looked at something, but they all had to have something in common to find the information that we have now.

- Why do we consider the atomic theory still a theory? What are the new developments- would love for you to share new sources here about what you find?

· The word "theory" in science doesn't mean a guess. It means an idea that has been very well confirmed and has stood the test of time. The same applies to biological evolution, which has stood the test of time even longer than relativity.
· The development of the atomic theory advanced greatly when chemistry became an exact science during the late 1700's. Chemists discovered that they could combine elements to form compounds only in certain fixed proportions according to mass. In 1803, a British chemist named John Dalton developed an atomic theory to explain this discovery. Dalton proposed that each element consists of a particular kind of atom and that the varying properties of the elements result from differences in their atoms. He further suggested that all atoms of a given element are identical in size, shape, and mass. According to Dalton's theory, when atoms combine and form a particular compound, they always combine in a specific numerical ratio. As a result, the composition by mass of a particular compound is always the same
- Why does it matter that we understand the structure of the atom?

· Because an atom is the basic unit of matter, so everything has atoms in it. We should know the structure, how they work, and what they contain because they forever surround us.