History of the Atom Timeline by Ashleigh Rains

Democritus (460 BC)

450

Democritus developed the concept of the 'atom'. He believed that everything in the universe was made of atoms and that these atoms where microscopic and indestructible. He thought the also had different sizes, shapes, and positions. He came up with these theories from his observations. Walker, Jim. "History of Atoms." History of Atoms. E-prime, Sept. 1988. Web. 26 Feb. 2014. History of the atom

Aristotle (348 BC)

450

Aristotle thought the atomic idea wa worthless. He thought matter was made of "Four Elements" (earth, fire, water, and air). He didn't believe in atoms or the atomic theory. Walker, Jim. "History of Atoms." History of Atoms. E-prime, Sept. 1988. Web. 26 Feb. 2014. Marks, Tracy. "Elemental: The Four Elements." Elemental: The Four Elements. N.p., 1998. Web. 27 Feb. 2014.

Dalton

Feb 28, 1800

Dalton found that matter consisted of atoms. He didn't know about it's structure. His theories stated the general information on the atom. Dalton performed experiments with various chemicals that showed matter consisted of atoms. "Lecture." Lecture. N.p., n.d. Web. 27 Feb. 2014. Walker, Jim. "History of Atoms." History of Atoms. E-prime, Sept. 1988. Web. 26 Feb. 2014.

Thomas

Jan 26, 1897

Thomas discovered the electron. He knew these electrons had negative charges and thought matter must have a positive charge. He gathered evidence from his experiments . He built a glass tube in which he shot rays which passed thorugh a vacuum. The rays seemed to come from the surrounding area of the nucleus. "Atomic Models Webquest." Atomic Models Web Quest. N.p., n.d. Web. 27 Feb. 2014. Walker, Jim. "History of Atoms." History of Atoms. E-prime, Sept. 1988. Web. 26 Feb. 2014.

Rutherford

Feb 28, 1911

Rutherford thought that electrons had to exist somewhere in the empty space around what we now know is the nucleus. (Which he discovered and named in 1919). He finally identified the partices of the nucleus as positive charges of matter, which he named protons. Rutherford got his evidence from experiments. He bombarded atoms with alpha rays and noticed some shot back and in odd directions. Walker, Jim. "History of Atoms." History of Atoms. E-prime, Sept. 1988. Web. 26 Feb. 2014.

Bohr

Feb 28, 1912

Bohr thought that electrons didn't spiral into th nucleus. Thought electrons could only orbit at certain allowed distances from the nucleus and the energy was purportional to distance from nucleus (more distance more energy). The light absorbed when an electron jumps to higher orbits and omitted when an electron
falls into lower orbit. He created his theories from observation. Walker, Jim. "History of Atoms." History of Atoms. E-prime, Sept. 1988. Web. 26 Feb. 2014.

Heisenberg and Schrodinger

Feb 28, 1930

Heisenberg and Schrodinger stated that the nucleus was made of neutrons and protons. They also came up with the electron cloud. They are also known for the uncertainty principle. The more precisely the position is determined, the less precisely the momentum is known in this instant, and vice versa. They used mathematical models. "Timeline of the Atom." : Erwin Schrodinger. N.p., n.d. Web. 27 Feb. 2014. Walker, Jim. "History of Atoms." History of Atoms. E-prime, Sept. 1988. Web. 26 Feb. 2014.