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Oxygen
In the late eighteenth century, Joseph Priestley conducted several experiments to determine if air was a singular substance, or made up of different gases. Priestley observed the creation of gas when mercury was heated. French chemist Antoine Laurent Laviose heard of Priestley's discovery and coined the element "oxygen". -
John Dalton's Atom
John Dalton theorized that the known elements must be made up of smaller particles. He discovered and published what he called "atomic weights", or the constant weights of one particle of each element. -
Humphry Davy's Battery
Humphry Davy was working with batteries when he realized that sending an electric charge through the compound potash created potassium. His discovery and later experiments opened the door to electrochemistry, or the idea that electricity could create chemical reactions. -
Molecules and Complex Substances
Italian physicist Amedeo Avogaro discovered that gases were not all made of individual particles, and that some were actually made of several atoms bonded together in specific ways. We now know these complex particles as molecules. -
The First Synthesis
Before 1828, it was assumed that compounds found in living beings, called organic compounds, were somehow different from nonliving substances, or inorganic compounds. Friedrich Wohler was attempting to combine two inorganic elements, ammonium and cyanide, to create another inorganic compound. But, to his shock, they combined to form the organic compound urea, which is produced as waste in most animal bodies. -
Visual System of Molecular Structure/Discovery of Ring Molecules
August Kekule devised the first simple way of drawing the atomic structure of molecules. He drew molecules as chains of atoms linked together. However, one chemical, called benzene, didn't mathematically fit his formula. The chain it created didn't have enough power to keep itself together. One night, Kekule had a dream about a snake eating its own tail, and he realized that benzene was like that snake; it formed a circle to connect to itself. -
Plastics
John Westley Hyatt was attempting to synthesize a material to make billiard balls when he created celluloid, a polymer derived from the stringy cellulose particles found in plants. This polymer was not only versatile in and of itself, but it also jumpstarted thousands of unique plastics created from the simple cellulose chemical. -
The Periodic Table of Elements
Dimitri Mendeleev was a Russian chemist who had set out to write his own textbook to help his students better understand the elements. When he arranged all 63 known elements based on their atomic weights and numbers, he found seven distinct groups of similar elements. He was even able to predict the discovery of new elements based on the holes in his arrangement. His discovery of elemental groups and relationships became known as periodic law. -
The Color of Fire
Robert Bunsen was fascinated with the different colors produced when he burned various substances. He concluded that the flame's color indicated what elements were present in the substance. He and his assistant, Gustav Kirchhoff, developed the first spectroscope to observe these colors, using a prism to scatter different flames into visible spectrums. Each element had a unique color spectrum when burned, which allowed them to discover two new elements: cesium and rubidium. -
Radioactivity
French scientist Henri Becquerel discovered that uranium was a source of strong radiation when it consistently caused objects to project silhouettes onto photo paper. Later on, Marie and Pierre Curie studied uranium extensively with the goal of isolating the specific particles that caused its radioactivity. This led them to the discovery of two new elements and an accurate means of detecting and measuring radioactivity. -
Electrons
Joseph Thomson conducted a series of experiments that allowed him to observe and estimate the charge within atoms, which helped him isolate and extract tiny, negatively charged particles from atoms. These particles were identical to the cathode rays Thomson had previously worked with, which led him to conclude that these rays were made up of electrically charged sub-atomic particles. These particles, now known as electrons, were the first sub-atomic particles ever discovered. -
Chemical Bonds
Gilbert Lewis was the first to propose an atomic model that explained the atom's tendency and ability to bond with other atoms. He suggested that the electrons within atoms are responsible for bonding because they existed farther away from the center of the atom. In Lewis' model, electrons orbited around the nucleus but were not attached to it, so they could also interact with the electrons of other atoms, forming pairs. This is what causes bonding to occur. -
Radioactive Decay
Scientist Ernest Rutherford built on the discoveries made by the Maries by isolating three specific types of radiation. He observed that radioactive material spontaneously released two types of charged particles, which he dubbed alpha and beta particles, as well as a unique electromagnetic radiation he called gamma rays. -
Fullerenes
Richard E. Smalley, Robert Curl, and Harry Kroto, three scientists at Rice University, were studying the structure of carbon in space when they came across something odd. They observed soccer ball-shaped molecules comprised of sixty carbon atoms each. These molecules were perfectly stable and refused to interact with other atoms. The discovery of this complex geometric figure led to the synthesis of countless different carbon allotropes, each with its own unique medical use.