-
460 BCE
Democritus
Stated that the world is made of small particles named atomon. They only differ in shape, arrangement, position, and magnitude.The Void, and atoms are the only things that exist. -
384 BCE
Aristotle
Stated that matter was made of four elements: Fire, Water, Air, and Earth. Matter also only had four properties: Hot, cold, dry, and wet. -
Period: 1492 to 1502
Columbus's Voyage
-
Lavoisier
Named oxygen, and proved the Law of Conservation of Mass. Also replaced the Phlogiston theory with the Theory of Oxygenation. -
Period: to
Revolutionary war
-
Dalton
Performed experiments that led to acceptance of atoms. This helped to state that all matter is made of atoms, small uncuttable, and indestructible particles. All atoms of one element are alike, while different element atoms are different. -
Avogadro
Developed the Mole, which is also known as Avogadro's number. It is the number of molecules in a single gram molecule. Also contributed a distinction between atom and molecule. -
Berzelius
Developed a way to advance chemical nomenclature, which allowed him to name any compound regularly. Also developed a system of notation that shows the compositions of any compound. The system had Latin names of the elements, and applied superscripts to designate atom numbers in each element. -
Period: to
Civil War
-
Plum Pudding Model
-
Thomson
Discovered that electrons are in an atom. Theorized that atoms are positive, and that they have electrons inside of them. -
Curie, M
Discovered radioactivity, which led to the x-ray. She also found out that radioactive particles cause atoms to break down. -
Planck
Developed Planck's constant, which was the relationship between the energy of a photon, and its frequency. The constant was a formula relating the energy of the radiation to the frequency. He also found out that oscillators emitted energy in parts, which would have the hv proportional to frequency. -
Rutherford's model
-
Rutherford
Proved that atoms are not filled with electrons by firing charged positive at gold foil. He theorized that atoms have a small positive center, the nucleus. He also stated that the nucleus is small compared to the atom, because an atom is mostly open space. -
Millikan
Determined the charge of an electron. Many results were multiples of a single number, the electron's charge. Also verified the photoelectric effect and used that information to find Planck's constant. -
Sinking of the Titanic
-
Moseley
Found relationships between lines in an x-ray spectra. The frequencies were proportional to the squares of whole numbers that are equal to the atomic number, plus a constant. This became known as Moseley's Law, which has helped to identify atoms. -
Bohr's "Solar system" Model
-
Bohr
Proposed that electrons moved in orbital shells. Outer shells contained higher energy, which determined the element's chemical properties. Also explained that element spectral lines were from electrons releasing energy to jump to higher or lower orbits. -
Period: to
World War 1
-
Heisenberg
Developed a theory of quantum mechanics that led to the discovery of allotropic forms of hydrogen. Also states a principle of uncertainty, which detailed that determining the position and momentum of a moving particle contain errors which can't be skipped when studying atoms. -
Schrodinger
Produced papers that start foundations to quantum wave mechanics. Explained how electrons move in wave form, and his Schrodinger equation also helped to describe the quantum state of a system that changes over time. -
Chadwick
Discovered the neutron. This was found when an unknown radiation with a neutral charge came out of beryllium. The knowledge of the neutron eventually leads to fission, and the atomic bomb. -
Period: to
World War 2
-
Mother's birth
-
Father's Birth
-
My birth
-
Modern day model
