Chem History

People who helped create the periodic table

Paraclesus

Early 1500s, encouraged chemically based medicine, he was an alchemist, meaning he mixed things without rhyme or reason (NOT an ideal method). Said you can heat/change substances into different products

Robert Boyle

1661, questioned fire, water, air, Earth, alchemy, wanted to know what substances were made of. He was the first to do quantitative experiments: trapped air in a J shaped tube, added mercury, found using graphing and data that as volume increased, pressure decreased

George Stahl

1700s, phlogiston theory: combustible materials release a fiery substance when burned, and if they don’t burn, they don’t have phlogiston, if they do burn, the phlogiston burns into the air

Antonie Lavosier

1789, In a closed system, found that matter is not created nor destroyed

Joseph Proust

1799, law of constant composition, given compound fixed composition by mass, chemically analyzed compounds from different sources (a block that’s 10 grams of one substance and 100 grams of the same will have the same percentage of material)

John Dalton

1803-08, law of multiple proportions (when 2 elements combine to form more than one compound masses of one element that combine with a fixed mass of the other element are in a ratio of small whole numbers). Ex CO has 12g carbon, 16g oxygen, CO2 has 12g carbon, 32g oxygen

Amadeo Avogadro

1811, equal gas volumes have equal molecules under the same conditions (Avogadro’s law), at the same temp and pressure H2 can exist as a molecule, not just a single atom

Michael Faraday

1830s, electricity and chemical change connected, laws of electrolisis, amount of substance changed at electrode depends on the electric charge passed, more charge=more chemical change (quantitative)

Henri Becquerel

1896, some atoms release radiation spontaneously, natural radioactivity doesn’t depend on combustion, heat, or ordinary chemical reactions

JJ Thompson

1856-1940, researched cathode ray tubes, 1st to discover electrons, came up with mass spectrometer (knock N with x-ray, get a cation, magnetic field launches it), objects with less mass get deflected more, found out which object had more mass with deflection, helped find isotopes (how we started organizing the periodic table)

Plum pudding model (Thompson)

Accepted theory of atoms, an even distribution of positive charges with negatives mixed in, not very dense

Robert Millikan

1868-1953, measured charge of electron. Oil drop experiment: x-rays ionize oil, usually drops fall but if you get magnetic fields just right one can be suspended, find charge by working backwards from the suspended drop

Ernest Rutherford

Father of radiation, showed 3 types of radiation: beta (atom, nucleus launches non-stable electrons, attached to positive plate), alpha (helium nucleus launched from atom, protons attached to negative plate), and gamma (like x-rays, high energy radiation). Wanted to prove plum pudding model: but through gold foil experiment found that atoms mass and charge were not spread evenly: found the nucleus.