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440 BCE
Democritus
Theorized about the atom, theorized how atoms move/stick together/make up everything and conducted his own experiment about splitting atoms with a seashell. Thought solid material atoms had hooks that made them stick together, then thought that they were wet and slippery, allowing them to slip past each other. -
John Dalton
Experiments with gases that first became possible at the turn of the nineteenth century. Matter is made up of atoms that are indivisible and indestructible. All atoms of an element are identical. Atoms of different elements have different weights and different chemical properties. Atoms of different elements combine in simple whole numbers to form compounds. Atoms cannot be created or destroyed. When a compound decomposes, the atoms are recovered unchanged. -
Alfred Nobel
Nobel persevered with his goal of developing a safe nitroglycerin explosive, first inventing the blasting cap and then discovering that a siliceous earth, kieselguhr, would stabilize nitroglycerin, thus making dynamite. -
William Crookes
Crookes paved the way for many discoveries. He worked as a Scientist in his own laboratory in London where he did all of his research and developed a range of different types of high vacuum tubes. -
Erwin schrodinger:
took the Bohr atom model one step further. Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position.
Discovery: an electron in an atom would move as a wave. he wrote a revolutionary paper that highlighted what would be known as the Schrödinger wave equation.
Atomic model: used mathematical equations to describe the likelihood of finding an electron in a certain position. -
J.J, Thomson
J.J. Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. Thomson's plum pudding model of the atom had negatively-charged electrons embedded within a positively-charged "soup." Rutherford's gold foil experiment showed that the atom is mostly empty space with a tiny, dense, positively-charged nucleus. Based on these results.
Atomic Model: the nuclear model of the atom. -
Marie Curie
Separated a lot of mineral pitchblende and got to discover and isolate radium and polonium. -
Ernest Rutherford
every atom contains a nucleus where all of its positive charge and most of its mass are concentrated. They deduced this by measuring how an alpha particle beam is scattered when it strikes a thin metal foil.
Discovery: every atom contains a nucleus where all of its positive charge and most of its mass are concentrated.
Atomic Model: Thin Metal Foil -
RA Millikan
The oil drop experiment, to determine the charge of an electron.
Discovery: photoelectric effect.
Atomic Model: electrons became negative -
Niels Bohr
Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. He was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element. The Bohr model shows the atom as a small, positively charged nucleus surrounded by orbiting electrons. -
Erwin Schrodinger
Neils Bohr, a student of Rutherford's, developed a new model of the atom. He proposed that electrons are arranged in concentric circular orbits around the nucleus.
Atomic Model: is patterned on the solar system and is known as the planetary model. -
James Chadwick
Discovered the neutron.
Chadwick's findings were pivotal to the discovery of nuclear fission, and ultimately the development of the atomic bomb.