-
Period: 100 to
Atomic Models
-
335
Aristotle and the Alchemists 335 B.C.
Aristotle was an alchemist who taught people that the Earth was made up of Water, Earth, Fire, and Air. This theory was more popular than Democritus' theory but was wrong. -
400
Plato 400 B.C.
Plato had the same beliefs as Aristotle. He came up with the word element, which is what Water, Fire, Earth, and Air became known as. -
430
Democritus 430 B.C.
Democritus was a Greek philosopher who began the search for a description of matter, He wondered if matter could be divided into smaller and smaller peces forever or if there was a limit to it. His theory was that smallest piece was possible and that it was undivisible. He named it "atomos" which is Greek for 'not to be cut'. He also believed they were small hard particles made up of the same material but were different shapes and sizes. His theory was ignored for over 2,000 years. -
Lavoisier
Antoine Lavoisier created the Law of Conservation of Mass, which states that matter can be changed from one form into another, mixtures can be seperated or made, and pure substances can be decomposed. No matter what, the total amount of mass stays the same. -
John Dalton
Dalton believed all elements were composed of atoms and that atoms were indivisible, indestructible particles. He also thought that atoms of different elements were different, ones of the same element were the same, and that compounds are formed by the joining of atoms of two or more elements.
This became one of the foundatons of modern chemistry. -
Dmitri Mendeleev
Dmitri Mendeleev is the man who created the periodic table, however it has improved and increased in size, he was the man who created it with his own ideas and plans. It was made accordinng to increasing order of the atomic weight of each known element starting with helium- the lightest- and ending with Bismuth. The table was published in 1869. -
J.J. Thomson
He provided the first hint that an atom is made of smaller particles. He proposed a model of the atom which is oftenreferred to as the "Plum Pudding Model". He believed atoms were made from a positively charged substance with negetavely charged electrons scattered about it -
Albert Einstein
Einstein's Theory of General Relativity predicted that the space-time around Earth would be warped and twisted by the planet's rotation. He determined that the laws of physics are the same for all non-accelerating observers and that the speed of light in a vacuum was independent on the motion of all observers, this is called the Theory of Relativity. -
Ernest Rutherford
He conducted an experiment where he fired a stream of tiny positively charged particles at a sheet of gold foil. Most of the particles passed through without changing course, however some bounced because positive repels positive. This meant the gold atoms were mostly open space. He concluded that an atom has a small,dense,positively charged center which he named the nucleus. He figured out the positive particles were in the center with the negative particles surrounding the nucleus. -
Solar System Atomic Model
Proposed by Bohr and Rutherford, also known as the Rutherford-Bohr Model. It suggests an electron orbits the nucleus like the planets do -
Niels Bohr
In Bohr's model each electron is placed in a certain energy level. According to Bohr, electrons move in definite orbits around the nucleus. These orbits are located at certain distances from the nucleus. -
Henry Moseley
Moseley was a British chemist who studied under Ernest Rutherford and developed the application of X-ray spectra to study atomic structure. This resulted in a more developed and advanced placement of the elements of Dmitri Mendeleev's Periodic Table by determination of atomic numbers which was based off of Antonious van den Broek's hypothesis that atomic number might be the amount of charge in an atom's nucleus. -
Electron Cloud, Schrodinger
This theory proposed that a dense nucleus is surrounded by clouds of electrons all at different levels in the orbitals.
