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Antoine Lavoisier
He found that in an ordinary chemical reactions, matter can be changed in many ways but it cannot be created or destroyed. This proposal is known as the law of conservation of mass. -
Joseph Proust
Proust observed that specific substances always contain elements in the same ratio by mass. This is known as the law of definite proportions. For example, the ratio of hydrogen to oxygen in water is always 2 hydrogen atoms per oxygen atom no matter the mass of the substance of water. -
J.L. Gay-Lussac
He studied gas reactions at constant temperatures and pressures. He realized that under constant conditions the volumes of reacting gases and gaseous products are in the ratio of small whole numbers -
John Dalton
Dalton studied Lavoisier and Proust and formed the basic atomic theory. He stated that all matter is composed of small particles called atoms, the atoms can't be broken down into smaller particles, all atoms are exactly alike, atoms can combine in simple ratios to form compounds, and all atoms of a particular element must have the same mass. -
John Dalton cont.
Dalton also came up with the law of multiple proportions. This states that the ratio of masses of one element that combine with a constant mass of another element can be expressed in small whole numbers. -
Amadeo Avogadro
Avogadro's hypothesis was similar to Gay-Lussac's hypthesis, seeing that they both involved gasses in constant temperature and pressure. Avogadro stated that the equal volumes of gases, under the same conditions, have the same number of molecules. -
J.J. Thomson
Thomson researched cathode rays which are rays that traveled toward th anode from the cathode. He discovered that cithode rays have electrons. He also measured the bending of the cathode ray path and from this he determined tha ratio of the electron's charge to its mass. -
The Curies
Pierre Curie and Marie Curie stated that radioactive materials cause atoms to break down spontaneously, releasing radiation in the form of energy and subatomic particles. -
Max Planck
PLanck stated that that energy is radiated in small discrete units called quanta -
Robert Millikan
Millikan, who was a scientist from America, was the first person to accuratly measure the electron's charge. In order to do this, he used a device that used oil, a battery, and charged plates. With his research and Thomson's, it was found that the electron's mass is 1/1837. -
Henry Moseley
Henry Moseley figured out that the number of protons determines the identity of the element and the number of neutrons determines the isotope of the element. He figured this out by using X-rays in X-ray tubes. He found that the wavelength of the X-rays depended on the number of protons in the of the atom, and is always the same for a given element; therefore the mass difference of isotopes are due to the number of neutrons in the nucleus. -
Lord Rutherford
Lord Rutherford was the first to predict there was something else in an atom (1920). Walter Bothe collected the first evidence of the neutron (1930). James Chadwick found high energy particles that had no charge when he repeated Bothe's work (1932). He called these particles a neutron. -
Erwin Schroedinger
Erwin discovered that the electrons moved in waves. -
Walter Bothe
Walter Bothe collected the first evidence of the neutron (1930). -
James Chadwick
James Chadwick found high energy particles that had no charge when he repeated Bothe's work (1932). He called these particles a neutron. -
Murry Gell
He was creditied for classifying subatomic particles and proposed the existence of quarks.
