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Democritus's Atomic Theory (492 B.C)
Democritus discovered that all objects are made of little things that are indivisible and indistructible. He called these things "atoms". Unfortunately, he could not provide chemical evidence and many scientists doubted this theory. -
Aristotle's Discovery of Matter (332 B.C.)
Aristotle concluded that everything is composed of matter that can only be changed by growth, decay, or motion. He also believed in the five elements fire, water, earth, air, and aether. -
Discovery of the Cell
Robert Hooke was working with a partner in a lab when he discovered tiny "cells" on a piece of cork. He then called these things "cells". -
Dalton's Atomic Theory
Dalton was a chemist that added onto Democritus's atomic theory. In short, all elements are created from indestructable particles called atoms. All different elements have different atoms. Also, he introduced the theory of compounds, in which different elements would combine and make a new element. -
Cathode Ray Tube
In 1859, J. Plucker built one of the first gas discharge tube. -
Thallium and Helium
In 1861, William Crooke discovered a previously unknown element with a bright green emission line in its spectrum and named the element thallium, from the Greek thallos, a green shoot. Crookes also identified the first known sample of helium. -
First Perodic Table
The Russian chemist by the name of Dimitri Ivanovich Mendelev developed the first periodic table, which displayed the details on every chemical element. -
The Void Theory
James Clerk Maxwell proposed electric and magnetic fields filled the void. -
Study of Canal Rays
E. Goldstien used a Cathode Ray Tube to study "canal rays" which had electrical and magnetic properties opposite of an electron. -
Discovery of the Electron
G.J. Stoney discovered that electricity was made of negative particles called electrons. -
X-Rays
In 1895 Wilhelm Roentgen discovered the existence of X-rays. -
Discovery of the Electron
In April, 1897, J.J. Thomson discovered that there are particles nearly 1000 times smaller than an atom. He called these particles "corpuscles", but they were later renamed to "electrons". -
Polonium and Radium
In the year 1898 the Curie's discovered two radioactive elements, Polonium and Radium. -
The Planck
In 1899, Max Planck proposed the smallest unit of time in which he called the planck. -
The Quanta Idea
In the year 1900, Max Planck explained hot glowing matter. He called this the idea of Quanta. -
Gamma Rays
In 1903, Rutherford named a certain type of radiation that a French chemist discovered. He named it Gamma ray. It went along with his previous Alpha and Beta rays. -
E=mc2
In 1905, Albert Einstien published the equation E=mc2. -
The Gieger Counter
Hans Gieger developed an electrical device used to find alpha particles and "click" when near it. -
The Atomic Bullet
In 1911, Ernest Rutherford came to the conclusion that the nucleus was very dense, and positively charged. He also concluded that electrons were outside the nuclus. He discovered this by using alpha particles as atomic bullets. -
Moseley's Law
In 1913, Henry Moseley created Moseley's law, which was the mathematical relationship between the wavelengths of the X-rays produced and the atomic numbers of the metals that were used as the targets in X-ray tubes. -
The Bohr Model
In 1913, Niels Bohr introduced the Bohr model, which was used to display information about atoms. -
Discovery of Isotopes
Through mass spectrograph, Aston discovered isotopes. -
Discovery of the Neutron
James Chadwick used alpha particles to discover a neutral atomic particles that was similar to an electron. This was called the neutron. -
Atomic Energy
Enrico Fermi conducted the first chain reaction that released energy from an atoms nucleus. -
Ramstein Incident
It took place in front of 300,000 people. The airforce display team collided during their display. 67 died and 346 were injured by the plane explosion and fire.