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500 BCE
Plato
Plato's most famous finding was his theory of Forms. This is a theory of metaphysics that claims that the material world is a copy of a more real, spiritual realm. -
400 BCE
Democritus
Democritus' major contribution to atomic theory was proposing that all matter is composed of tiny, indivisible particles called "atoms,". This also means "indivisible" in Greek. This is the first recorded concept of the atom as the fundamental building block of matter. Democritus believed these atoms were solid, differed in size and shape for the various properties. -
384 BCE
Aristotle
One of Aristotle major accomplishments was the discovery of the earth being round. From his observations of the shape of the shadow the Earth caused on the Moon during a lunar eclipse. He also was the first known to theorize that the Earth was the center of the universe. -
Robert Boyle
Robert Boyle's most major finding is known as Boyle's Law. It claims that the volume of a gas is inversely proportional to its pressure. Demonstrating that as pressure increases, volume decreases, and vice versa while the temperature remains constant. This law is considered a foundational concept in chemistry. -
The Alchemists
The primary goal of alchemists in their experiments was to combine base metals, such as lead, into gold. They would search for a mythical substance called the "philosopher's stone" that could facilitate this transformation. This was around the Middle Ages in Europe. -
John Dalton
One of John Dalton's major finding was the development of the modern atomic theory. It states that all matter is made up of tiny, indivisible particles called atoms. And each element has its own unique type of atom, and that atoms of different elements combine in simple whole numbers to form compounds. John Dalton helped laid the foundation for modern chemistry -
Newland's Law of Octaves
The law of octaves, created by John Alexander Reina Newlands, is a conclusion that states that when chemical elements are arranged in order of increasing atomic weight, the properties of every eighth element are similar to the first. -
Mendeleev's Pd. Table
The Mendeleev's Pd. Table was created by Dmitri Mendeleev. He arranged the elements in order of atomic mass. It is the number of times heavier an atom is than one-twelfth of a carbon-12 atom. His Pd. Table is very important because it's used a lot in experiments and chemical reactions. -
Photoelectric Effect
Heinrich Hertz discovered that when light shines on a metal, electrons can be ejected from the surface of the metal in a phenomenon. This is called the photoelectric effect. -
Discovery of Radioactivity
A French man named Becquerel accidentally found that uranium salts emit a penetrating radiation. Noticed that it could be recorded on a photographic plate, marking the discovery of radioactivity. -
Planck's Quantum Theory of Light
Max Planck's law created a new idea of the nature in the light. It illustrates that light exists as tiny massless particles called photons. They show wave-particle duality, which have some properties of both a particle and a wave. -
Plum Pudding Model
J.J. Thomson's was experimenting with cathode ray tubes when they showed that all atoms contain tiny negatively charged subatomic particles or electrons. Thomson proposed the plum pudding model of the atom, which had negatively charged electrons embedded within a positively charged. -
Robert Millikan
Robert Millikan is most well-known for his "oil drop experiment". This experiment accurately determined the charge of a single electron. And is a significant contribution to atomic physics. Millikan's experiment proved that the charge of an electron is a discrete value, not a continuous range. -
Rutherford's Gold Foil Experiment
Ernest Rutherford gold foil experiment involved positively charged alpha particles at a thin sheet of gold foil. Showing that most particles passed straight through, while a small number were deflected at large angles. This led to the conclusion that atoms have a tiny, dense, positively charged nucleus at their center and are mostly empty space. This discovery significantly changed the understanding of atomic structure. -
Bohr's Planetary Model
Bohr's planetary model, also known as the Bohr model, describes an atom being a small and dense nucleus surrounded by electrons. While orbiting in fixed, circular paths, called energy levels. This discovery developed the key concept that electrons can only occupy specific energy levels and not in between them. -
Mosley's Atomic Numbers
Henry Moseley's atomic number refers to the concept that the atomic number of an element is directly related to the number of positive charges in its nucleus. This allowed for a more accurate arrangement of elements on the periodic table. -
Discovery of the Proton
The discovery of the proton was discovered by Ernest Rutherford. He proved that the nucleus of the hydrogen atom is present in the nuclei of all other atoms. -
Schrodinger Equation
The wave equation created by Erwin Schrödinger; equation describes the form of the probability waves. That governs the motion of small particles, and it specifies how these waves are altered by the environments. The Schrodinger equation is essential because, it forms the basis for much of modern physics, chemistry and material science. And used to understand the electronic structure of atoms and molecules. -
Heisenberg Uncertainty Principle
Made by the German physicist and Nobel laureate Werner Heisenberg in 1927, the uncertainty principle states that we cannot know both the position and speed of a particle. Since the photon or electron, with perfect accuracy of the position the less we know about the speed -
Discovery of the Neutron
James Chadwich put beryllium with alpha particles from polonium, producing a neutral radiation. Once directed at paraffin wax, it ejected protons, confirming the existence of a neutral particle with a mass similar to a proton, which he named the neutron.