-
350
Aristotle (BC)
Aristotle believed that there were 5 elements: Fire, Earth, Air, Water, and Aether. Fire is dry and hot. Earth is cold and dry. Air is wet and hot. Water is wet and cold. Aether is divine and makes up heavenly bodies. This contradicts what Democritus believed because Aristotle thought that there were 5 elements instead of an infinite amount. -
350
Aristotle (BC)
Aristotle believed that there were 5 elements: Fire, Earth, Air, Water, and Aether. Fire is dry and hot. Earth is cold and dry. Air is wet and hot. Water is wet and cold. Aether is divine and makes up heavenly bodies. This contradicts what Democritus believed because Aristotle thought that there were 5 elements instead of an infinite amount. -
400
Democritus (BC)
Everything is made of atoms, which are indivisible physically, but not geometrically. There is empty space between atoms. Atoms cannot be destroyed. There are an infinite number of atoms. There are an infinite number of kinds of atoms which have different sizes and shapes. Atoms are solid and have a shape that is similar to their properties. Atoms are connected mechanically; some have hooks, others have sockets and balls. -
400
Democritus (BC)
Everything is made of atoms, which are indivisible physically, but not geometrically. There is empty space between atoms. Atoms cannot be destroyed. There are an infinite number of atoms. There are an infinite number of kinds of atoms which have different sizes and shapes. Atoms are solid and have a shape that is similar to their properties. Atoms are connected mechanically; some have hooks, others have sockets and balls. -
Antoine Lavoisier
He found Oxygen and Hydrogen. He helped create the first list of elements. He also established Sulfur as an element and discovered conservation of mass. -
Antoine Lavoisier
He found Oxygen and Hydrogen. He helped create the first list of elements. He also established Sulfur as an element and discovered conservation of mass. -
John Dalton
Elements are made up of atoms. Atoms of a certain element have the same mass and size. Atoms of other elements have different sizes, masses and properties. Atoms cannot be subdivided, destroyed or created. Atoms of 2 or more elements can be combined in whole number ratios to create compounds. Chemical reactions combine, separate, or rearrange atoms. This improved upon earlier ideas because atoms can be combined to form compunds. -
John Dalton
Elements are made up of atoms. Atoms of a certain element have the same mass and size. Atoms of other elements have different sizes, masses and properties. Atoms cannot be subdivided, destroyed or created. Atoms of 2 or more elements can be combined in whole number ratios to create compounds. Chemical reactions combine, separate, or rearrange atoms. This improved upon earlier ideas because atoms can be combined to form compunds. -
Henri Becquerel
He discovered radioactivity. He investigated emission of nuclear radiation. This added radiation as a new property that different elements may or may not have. -
Henri Becquerel
He discovered radioactivity. He investigated emission of nuclear radiation. This added radiation as a new property that different elements may or may not have. -
Max Planck
He created the Planck black-body radiation law. This built upon what was already known about radiation. -
Max Planck
He created the Planck black-body radiation law. This built upon what was already known about radiation. -
J.J. Thomson
Thomson discovered electrons and isotopes. He found that Hydrogen only had 1 electron. This changed the entire model of the atom and laid the foundation for more discoveries. -
J.J. Thomson
Thomson discovered electrons and isotopes. He found that Hydrogen only had 1 electron. This changed the entire model of the atom and laid the foundation for more discoveries. -
Marie and Pierre Curie
They theorized about radioactivity and discovered nuclear energy. This helped others discover nuclear fission. -
Marie and Pierre Curie
They theorized about radioactivity and discovered nuclear energy. This helped others discover nuclear fission. -
Ernest Rutherford
Radioactivity is the disintegration of atoms. There are 3 types of radioactivity: alpha rays, beta rays, and gamma rays. A small nucleus is orbited by electrons. The Hydrogen nucleus is the building block of other atoms. Rutherford named it the proton. This changed the atomic model and explained radioactivity. -
Ernest Rutherford
Radioactivity is the disintegration of atoms. There are 3 types of radioactivity: alpha rays, beta rays, and gamma rays. A small nucleus is orbited by electrons. The Hydrogen nucleus is the building block of other atoms. Rutherford named it the proton. This changed the atomic model and explained radioactivity. -
Niels Bohr
He discovered electrons travel in orbits around the nucleus. Properties of the atom are determined by the amount of electrons around the nucleus. An electron can drop energy levels when emitting a photon, which was the basis for quantum theory. This changed the model of the atom and described why different atoms have different properties. -
Robert Millikan
Millikan discovered the charge of the electron which is negative. He calculated the charge of an electron to be 1.592e-19 coulomb. This better described what electrons are. -
Henry Moseley
He improved the periodic table of elements by fixing gaps and correcting the error between the atomic masses of Cobalt and Nickel. He ultimatley helped make the periodic table successful. -
Niels Bohr
He discovered electrons travel in orbits around the nucleus. Properties of the atom are determined by the amount of electrons around the nucleus. An electron can drop energy levels when emitting a photon, which was the basis for quantum theory. This changed the model of the atom and described why different atoms have different properties. -
Robert Millikan
Millikan discovered the charge of the electron which is negative. He calculated the charge of an electron to be 1.592e-19 coulomb. This better described what electrons are. -
Henry Moseley
He improved the periodic table of elements by fixing gaps and correcting the error between the atomic masses of Cobalt and Nickel. He ultimatley helped make the periodic table successful. -
Erwin Schrodinger
He created an equation which is named after him. He questioned the Copenhagen interpretation of quantum mechanics by proposing the cat problem. He challenged common practice and improved quantum mechanics. -
Erwin Schrodinger
He created an equation which is named after him. He questioned the Copenhagen interpretation of quantum mechanics by proposing the cat problem. He challenged common practice and improved quantum mechanics. -
Werner Heisenberg
He believed there were neutrons in the nucleus. His model of the atom shows this. This changed the atomic model once again. -
Werner Heisenberg
He believed there were neutrons in the nucleus. His model of the atom shows this. This changed the atomic model once again. -
James Chadwick
He discovered the neutron and helped lead to the discovery of nuclear fission. He definitively proved that neutrons did exist which cemented neutrons being in the nucleus as the accepted model. -
James Chadwick
He discovered the neutron and helped lead to the discovery of nuclear fission. He definitively proved that neutrons did exist which cemented neutrons being in the nucleus as the accepted model.
