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400 BCE
Democritus
Democritus' major discovery regarding the atom was the concept of "atomism," proposing that all matter is composed of tiny, indivisible particles called "atoms" which differ in shape and size, and that these atoms move through empty space, causing changes in matter by colliding and combining with each other; essentially laying the foundation for the modern atomic theory, despite not being able to experimentally verify his ideas -
335 BCE
Aristotle
Aristotle's major discoveries include the development of formal logic, particularly the syllogism system, which laid the foundation for reasoning and argument; his significant contributions to zoology by classifying animals and studying their behavior, essentially becoming known as the "father of zoology"; and his work in natural philosophy, exploring concepts like motion, causation, and the elements, including his theory of the four elements (earth, air, fire, and water). -
4 BCE
Plato
Plato's most significant contribution to philosophy is his "Theory of Forms," which posits that the physical world we experience is merely a shadow of a perfect, eternal realm of "Forms" representing the true essence of things like justice, beauty, and goodness; essentially proposing that true reality exists beyond our physical senses and can only be accessed through philosophical reasoning. -
Robert Boyle
Robert Boyle's major contribution to the development of the atomic theory was proposing that all matter is composed of tiny, indivisible particles called "corpuscles" and these particles could combine to form various substances, laying the groundwork for modern atomic theory; he also confirmed this idea through his work on gases, most notably discovering "Boyle's Law" which relates pressure and volume of a gas, further supporting the concept of matter being made up of tiny particles in motion. -
The Alchemists
The main goal od the alchemists in their experiments was to combine base metals, such as lead, into gold. They tried to find a mythical substance called philosophers stone that facilitated this transformation. This was the middle ages in Europe. -
John Dalton
John Dalton is most recognized for developing the "atomic theory," which proposed that all matter is made up of tiny, indivisible particles called atoms, with each element having its own unique type of atom, laying the foundation for modern chemistry; he also significantly contributed to the understanding of color blindness, which is sometimes called "Daltonism" due to his own experience with it. -
Newland's Law of Octaves
English chemist John Alexander Reina Newlands was the first to arrange the elements in a periodic table in order of increasing atomic mass. He noticed that every eighth element had similar properties and called this the law of octaves. The law of octaves is a generalization that states that when chemical elements are arranged in order of increasing atomic weight, the properties of the eighth element are similar to the properties of the first element. -
Mendeleev's Pd Table
Explanation: Mendeleev arranged elements on cards based on their atomic weight and noticed repeating patterns, leading to the creation of the periodic table. This discovery allowed him to predict the existence of undiscovered elements by leaving gaps in his table -
Photoelectric Effect
When light shines on a metal, electrons can be ejected from the surface of the metal in a phenomenon known as the photoelectric effect. This process is also often referred to as photoemission, and the electrons that are ejected from the metal are called photoelectrons. This was discovered by Heinrich Hertz. -
Discovery of Radioactivity
French physicist Henri Becquerel discovered radioactivity in 1896 while investigating uranium salts and X-rays. Becquerel noticed that uranium salts emitted a radiation that could be detected on photographic plates, even on cloudy days when the salts weren't exposed to sunlight. -
Planck's Quantum Theory of Light
Planck's Quantum Theory of Light is that light is not emitted or absorbed as a continuous wave, rather in discrete packets of energy called "quanta" or "photons," meaning that light behaves like particles with a specific energy level directly proportional to its frequency, a concept that revolutionized our understanding of light and laid the foundation for quantum mechanics. Planck's theory made a significant shift in physics, further developments in quantum mechanics. -
Plum Pudding Model
The plum pudding model was the first scientific model of the atom to describe an internal structure by J. J. Thomson in 1904. The model was about two properties of atoms then known that there are electrons, and that atoms have no net electric charge. There had to be an equal amount of positive charge to balance out the negative charge of the electrons. Thomson's model is popularly referred to as the "plum pudding model" because the electrons are distributed like raisins in a plum pudding. -
Robert Millikan
Robert Millikan's major discovery was the precise measurement of the charge of a single electron, which he achieved through his famous "oil drop experiment" around 1910, publishing his results in 1913; this experiment proved that the charge of an electron is a fundamental unit and not continuously variable, solidifying our understanding of atomic structure. The oil drop experiment, where tiny charged oil droplets were put between charged plates, allowing for precise measurement of their charge. -
Rutherford's Gold Foil Experiment
The Rutherford gold foil experiment was a scientific experiment by Ernest Rutherford where a beam of positively charged alpha particles were fired at a thin sheet of gold foil, revealing that most of the particles passed straight through, but a small number were deflected at large angles, leading to the discovery of the atomic nucleus and the understanding that most of an atom is empty space; this contradicted the previously held "plum pudding model" of the atom. -
Bohr's Planetary Model
Bohr's planetary model, also known as the Bohr model, describes an atom as a small, dense nucleus surrounded by electrons orbiting in fixed, circular paths called energy levels, similar to how planets orbit the sun, with the key concept that electrons can only occupy specific energy levels and not in between them. Each energy level corresponds to a specific energy value, meaning electrons can only occupy certain energy levels and not any position in between. -
Mosley's Atomic Numbers
Moseley's atomic numbers refer to the concept that the atomic number of an element, representing the number of protons in its nucleus, is the fundamental property that should be used to arrange elements on the periodic table, a discovery made by physicist Henry Moseley through his experiments with X-ray spectroscopy; he established that the atomic number, not atomic mass, is the answer in determining an element's position on the periodic table. -
Discovery of the Proton
The proton was discovered by Ernest Rutherford. He conducted experiments that proved the hydrogen nucleus, which he named the proton, is present in the nuclei of all other atoms, effectively discovering the proton -
Schrodinger Equation
Conceptually, the Schrödinger equation is the quantum counterpart of Newton's second law in classical mechanics. Given a set of known initial conditions, Newton's second law makes a mathematical prediction as to what path a given physical system will take over time. Newton's second law makes a mathematical prediction as to what path a given physical system will take over time. The Schrödinger equation gives the evolution of a wave function over time. -
Heisenberg Uncertainty Principle
uncertainty principle, statement, articulated by the German physicist Werner Heisenberg, that the position and the velocity of an object cannot both be measured exactly, at the same time, even in theory. The very concepts of exact position and exact velocity together, in fact, have no meaning in nature. -
Discovery of the Neutron
James Chadwick's discovery was based on experiments that involved firing alpha radiation at beryllium, which produced a penetrating radiation. He then observed the protons ejected from paraffin wax when it was struck by radiation. Chadwick predicted that the radiation was made up of uncharged particles with a mass similar to a proton, which he called neutrons