History of Matter

Best known for the pioneering work in the study of radioactivity which led to the discovery of the elements radium and polonium. Marie and Pierre worked at Pierre’s Laboratory in Paris, where they studied radiation coming from uranium compounds. Marie unexpectedly made the discovery that uranium pitchblende and the mineral chalcocite emitted four times as much radiation as expected = a small amount of unknown radiating element. Marie got a doctorate for her thesis of radioactive substances and together they won a Nobel Prize for the discovery of radioactivity.

*Observations/Experiments/Evidence – Used the study of cathode rays to determine that the matter that makes up the rays were not hydrodgen atoms (proposed by William Prout and Norman Lockyer), but smaller, negatively charged particles called corpuscles (electrons)
*Discoveries/Conclusions – Thomson proposed that these corpuscles made up an atom. He was also able to meausre the mass and charge of an atom, and developed the plum pudding atom model (electrons surrounded by positive matter).

Contribution – JJ Thomson's discovery of the electron greatly contributed to later models of the atom.

Observations/Experiments/Evidence – Led the Geiger-Marsden experiment with colleagues. This experiment demonstrated the nuclear nature of atoms by deflecting alpha particles passing through a sheet of thin gold foil. Led to the discovery of the nucleus.
Discoveries/Conclusions – Rutherford was the first person to knowingly split the nucleus, he discovered alpha and beta rays, set forth the laws of radioactive decay, and identified alpha particles as helium nuclei.
Contribution – Was a central physicist in the study of radioactivity step on of nuclear physics. He overturned Thomson’s plum-pudding model in 1911 with his gold foil experiment that showed the atom has a tiny, heavy nucleus. Rutherford Model showed most of atom was open space and offered no resistance to the passage of alpha particles and most of the mass of an atom is in the nucleus.

*Observations/Experiments/Evidence – Introduced idea of levels of electrons; Bohr improved on the theory made by Rutherford, who said that an atom has a nucleus center surrounded by a cloud of weightless electrons. This meant that as electrons lost energy, the electrons would spiral down to the nucleus in a small amount of time, which meant that all atoms were unstable.
*Discoveries/Conclusions – Niels Bohr establishes the theory that electrons were organized on levels based on the amount of energy they had. The only way an electron could gain or lose energy was by moving up or down energy levels within the cloud of electrons. He also proposed that electrons emit energy as radiation.
Contribution – Bohr’s theory advanced scientists’ understanding of atom and contributed greatly to the study of theoretical physics. The Bohr atom model explained the mechanics of atoms and behavior of elements based on the energy levels of an atom.

Experimented with the electron. Said the electron must move around a nucleus. Had ideas of an electron with the properties of a wave. Said an electron would behave under certain conditions as if it were radiant energy. Einstein agreed with Broglie’s work and eventually Broglie’s work reached scientists around the world.

Helped establish the Theory of Quantum Mechanics. His theory and application resulted in the discovery of allotropic forms of hydrogen. He said an electron always has a position in space at any given time. Was one of the first people to use matrix equations. He worked on plasma physics, thermonuclear processes, elementary particles, and Atomic Physics.

*Observations/Experiments/Evidence – Schrodinger liked the concept of atomic structure defying laws of conservation. He developed an eqaution to find an electron at a given point, thus creating the quantum mechanical model. He found inspiration from Niels Bohr's atomic model and studied under physicist Ernest Rutherford.

*Discoveries/Conclusions – Schrodinger develops his own theory that electrons orbited the nucleus of an atom as a cloud. The closer to the nucleus, the denser the cloud - a higher possibility of finding an electron at a given location.

Contribution – Schrodinger advances atomic theory. His idea of an electron cloud is accepted my many scientists today. He developed a mathematical equation (coined Schrodinger's Equation) that showed the wave-like behavior that atoms exhibited. This equation greatly advanced the field of quantum mechanics. His other well-known legacy of Schrodinger's Cat, is also an important contribution to science.

Made a fundamental discovery in the domain of nuclear science - he proved the existence of neutrons. Chadwick proposed that there were neutrons in the nucleus of an atom and that the weight of a neutron was similar to that of a proton. Prepared the way towards the fission of uranium and towards the creation of the atomic bomb. Won the Nobel Prize in Physics in 1935.

Worked on natural and artificial radioactivity, transmutation of elements, and nuclear physics. Did research on the action of neutrons on heavy elements, which was an important step to discover uranium fission. Was an advocate for science and chemistry, working as a professor and helped construct centers for studies of nuclear fission.

Discovered the radiationless transition called the Auger effect. After fleeing Germany during WW2 she moved to Sweden to continue her work. The experiments done there provided evidence for nuclear fission which eventually led to the Manhattan Project. Meitner was awarded the Nobel Prize in 1944 for her work in the field of chemistry.

Linus Pauling published a paper on his research on the chemical bonding between atoms. In his book, Pauling explained his idea of the alpha helix, which put proteins in a spiraling shape. Pauling's ideas influenced other scientists such as Watson and Crick, who discovered the double helix shape that DNA exhibited. He helped connect chemical bonds and their role in the structure of complex substances. Pauling is one of the main founders of quantum chemistry and molecular biology.

Responsible for much of the discovery work surrounding the structure of DNA. Was at first not allowed to work on the model, because she was a woman. With reluctance she convinced a higher scientist to let her work on the project and took what he called the most beautiful x-rays of the DNA model ever taken, she became very close to solving the DNA model.

He demonstrated how helium is continually produced during the process of radioactive decay in radium (a crucial importance to modern understanding of nuclear reactions). He also published several papers on the nitrogen oxides. He discovered the atoms argon, helium, neon, krypton, and xenon, making up the noble gases