Nataliac3

The Alchemists

500 BCE

The alchemists were a varied group of scholars and charlatans whose goal was two-fold: to create the Philosopher's Stone (which caused the transmutation of lead into gold) and the discovery of the Elixir of Life (bestowing immortality on the person who possessed it). The origin of the term “ alchemy ” is uncertain. https://courses.lumenlearning.com/cheminter/chapter/alchemy/#:~:text=The%20alchemists%20were%20a%20varied,term%20%E2%80%9C%20alchemy%20%E2%80%9D%20is%20uncertain.

Plato

427 BCE

He found that there are only five solid shapes whose sides are made from regular polygons (triangles, squares, pentagons, hexagons, etc) Plato was so impressed with this discovery that he was convinced that atoms of matter must derive from these five fundamental solids.

Democritus

400 BCE

Democritus believed that everything in the universe was made up of atoms, which were microscopic and indestructible.

Aristotle

330 BCE

Aristotle formalized the gathering of scientific knowledge.

Solar System Model

330 BCE

Plato first proposed that the planets followed perfect circular orbits around the Earth. Later, Heraclides. developed the first Solar System model, placing the planets in order from the Earth it was is now called the geocentric solar system model.

Robert Boyle

1662

Every general-chemistry student learns of Robert Boyle as the person who discovered that the volume of a gas decreases with increasing pressure and vice versa—the famous Boyle's law. A leading scientist and intellectual of his day, he was a great proponent of the experimental method.

Lavoisier

1789

Lavoisier found that the total mass of products and reactants in a chemical reactions is always the same. This led to the theory of the law of conservation of mass.

John Dalton

1803

Dalton discovered the total pressure of a mixture of gases amounted to the sum of the partial pressures that each individual gas exerted while occupying the same space.

Dmitri Medeleev

1869

Dmitri Mendeleev jotted down the symbols for the chemical elements, putting them in order according to their atomic weights and inventing the periodic table.

Photoelectric Effect

1887

photoelectric effect, in which electrically charged particles are released from or within a material when it absorbs electromagnetic radiation. The effect is often defined as the ejection of electrons from a metal plate when light falls on it.

The Curies

1896

In 1898 French physicists Pierre and Marie Curie discovered the strongly radioactive elements polonium and radium, which occur naturally in uranium minerals. Marie coined the term radioactivity for the spontaneous emission of ionizing, penetrating rays by certain atoms.

Solid Sphere of "Billiard Ball" Model

1897

The Solid Sphere, made by J.J. Thomson, is an atomic model proposed by John Dalton in 1803 stating that all objects are made of particles called atoms, and that they are solid spheres that cannot be divided further into smaller particles. This is similar to the model made by the Greeks in the fifth century BCE.

JJ Thomson

Apr 30, 1897

Thomson announced his discovery that atoms were made up of smaller components. This finding revolutionized the way scientists thought about the atom and had major ramifications for the field of physics.

Plancks Quantum Theory of Light

1900

Max Planck, a German physicist made this theory. Planck demonstrated that energy, in certain situations, can exhibit characteristics of physical matter.

"Plum Pudding" Model

1904

J.J. Thomson founded the "Plum Pudding" Model. The electrons as negatively-charged particles embedded in a sea of positive charge. The structure of Thomson's atom is analogous to plum pudding, an English dessert

Albert Einstein

1905

Albert Einstein is best known for his equation E = mc2, which states that energy and mass (matter) are the same thing, just in different forms.

Robert Millikan

1910

Robert Millikan succeeded in precisely determining the magnitude of the electron's charge. Small electrically charged drops of oil were suspended between two metal plates where they were subjected to the downward force of gravity and the upward attraction of an electrical field.

Ernest Rutherford

1911

He found that the atom consists mostly of empty space, with its mass concentrated in a central positively charged nucleus. He also discovered that there are two types of radiation. Alpha and Beta

Neils Bohr

1913

In 1913, Niels Bohr proposed a theory for the hydrogen atom, based on quantum theory that some physical quantities only take discrete values. Electrons move around a nucleus, but only in prescribed orbits, and If electrons jump to a lower-energy orbit, the difference is sent out as radiation.

Henry G.J. Mosely

1913

Henry discovered a systematic relation between wave- length and atomic number. This discovery is now known as Moseley's Law.

Werner Heisenberg

1925

Heisenberg developed a key piece of quantum theory, the uncertainty principle, and profound implications

Electron Cloud Model

1926

Thanks to this model, Erwin Schrodinger found that... electrons were no longer depicted as particles moving around a central nucleus in a fixed orbit. Instead, Schrodinger proposed a model whereby scientists could only make educated guesses as to the positions of electrons

Schrodinger Equitation

1926

Erwin Schrodinger made the equation that describes the form of the probability waves (or wave functions [see de Broglie wave]) that govern the motion of small particles, and it specifies how these waves are altered by external influences.

James Chadwick

1932

Chadwick made a fundamental discovery in the domain of nuclear science: he proved the existence of neutrons – elementary particles devoid of any electrical charge.