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Jan 25, 630
Democritus
Democritus was an ancient Greek philosopher who claimed everything is made of atoms, and that the atom was the smallest unit of matter. He is sometimes known as that father of modern science. -
Dalton Atomic Theory
This theory states that all matter is made of tiny particles that are unchanging. It also states that elements are characterized by the mass of the atom. -
John Dalton
John Dalton was an important chemist that came up with the law of conservation of mass, the law of define proportions, and the law of multiple proportions. He postulated that chemical reactions occur when atoms are rearranged. -
Law of Conservation of Mass
States that the mass of an isolated system will remain constant over time. This law was discovered by John Dalton. -
Law of multiple proportions
The law of multiple proportions says when two element combine to form more than one compound the mass of one element that combines with a given mass of the others is in the ratio of small whole numbers. -
Law of definite proportions
The law of multiple proportions says when two element combine to form more than one compound the mass of one element that combines with a given mass of the others is in the ratio of small whole numbers. -
Henri Becquerel
In 1908 Becquerel was elected Permanent Secretary of the Academie des Sciences. He died at the age of
55. The SI unit for radioactivity , the Becquerel (Bq), is named after him. -
J.J. Thomson
A British physicist and Nobel Laureate. Credited with discovering electrons and isotopes, inventing the mass spectrometer. -
Marie Curie
Marie Sklodowska-Curie was a polish physicist and chemist who is famous for her pioneering research
on radioactivity. She was also the first woman to win a nobel prize, and the only person to win it
in multiple sciences. Her achievements included a theory of radioactivity, techniques for isolating
radioactive isotope and the discovery of two elements, polonium and radium. -
Robert Millikan
Robert Millikan was an American experimental physicist and Nobel laureate in physics. This was for the
measurement of the charge on an electron and for work on the photoelectric effect. He is also known
for his works on the Oil Drop Experiment. -
Dmitri Mendeleev
Dmitri Mendeleev was a Russian chemist and inventor who created the first periodic table of elements. He also predicted some elements that were not yet discovered. -
Ernest Rutherford
New Zealand-born British chemist and physicist who became known as the father of nuclear physics. -
Erwin Schrodinger
In first years of his career he became acquainted with the ideas of Quantum Theory. This knowledge
helped him work on some problems in the statistical physics. The old quantum theory is a collection of
results from the years 1900-1925 which predate quantum mechanics. -
Cathode Ray Tube Experiment
In this experiment Thompson observed the deflection of cathode rays by an electric field. This experiment lead to the discovery of the electron. -
Plum Pudding Model
Thompson discovered that atoms were made of negative and positive charges and believed that the atoms structure was similar to plum pudding, in which the negative electrons floated in a positively charged “pudding.” This was proved incorrect by Rutherford’s model. -
Oil Drop Experiment
In 1908 Robert Millikan was a professor at the University of Chicago, and worked on the oil drop
experiment. This experiment measured the charge on a single electron. It also measured the force on
tiny charged droplets of oil suspended against gravity between two metal electrodes. Millikan showed
the results could be explained as integer multiples of a common value (1.592 x 10^-19) charge of a single
electron. -
Rutherford Gold Foil Experiment
Also called Geiger-Madsen experiment. An experiment to probe the structure of the atom, performed by
Hans Geiger, Ernest Madsen in 1909 under direction of Ernest Rutherford. This experiment showed that atoms hasd nuclei -
Gold Foil Experiment
Diffraction of alpha particles (helium nuclei containing two positive charges) by a thin foil made of gold
metal. Opposite side is zinc sulfide screen that emits a flash of light when struck by an alpha particle. -
Rutherford Model
A very small charged nucleus containing much of the atoms mass was orbited by low mass electrons.
Contained new features of a relatively high central charge concentrated into a very small volume in
comparison to the rest of the atom. -
The Bohr Model
The Bohr Model is a model of an atom containing a small positively charged nucleus orbited by negatively charged electrons. -
Neils Bohr
Theorized that any atom could only exist in a discrete set of stable states. He also described the atomic structure in the Bohrs Atomic Model. He believed the energy of the orbit is related to its size. -
Quantum Mechanical Model
Also known as quantum physics or quantum theory. A branch of physics dealing with physical
phenomena at microscopic scales. Quantum mechanics departs from classical
mechanics. It also provides a mathematical description of much dual particle-like and wave-like behavior.
The quantum mechanical model is one of the two models of the atomic structure we use today. This model is based off the quantum theory, and its says matter also has properties associated wit
and interactions of energy and matter. -
James Chatwich
James Chatwich discovered the neutron. Neutrons help stabilize the atom. -
Murray Gell-Mann
Murray Gell-Mann was an American Physicist that came up with a new classification system for baryons called the eightfold way. He also discovered the quark, which is the building block for neutrons protons and matter.
