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Democritus, an ancient Greek philosopher, is credited with the earliest proposal of the atom as the fundamental building block of matter. Around 400 BCE, he postulated that everything in the universe is composed of small, indivisible particles called "atomos." Though his ideas were philosophical and not based on empirical evidence, they laid the foundation for later atomic theories. Democritus' atomic theory remained influential for centuries, despite being largely speculative at the time. -
In 1803, British scientist John Dalton developed his Atomic Theory, proposing that all matter is composed of indivisible atoms, that atoms of the same element are identical, and that chemical reactions involve the rearrangement of these atoms. His theory revolutionized chemistry, providing a clear explanation for the law of definite proportions and atomic weights. Dalton's work marked a major step in the establishment of modern chemistry. -
First Proposed: 1803
Superseded By: Thomson’s Plum Pudding Model
Change Date: 1897
Dalton's model was based on the idea that atoms are indivisible and solid spheres. -
The United States doubles its land because Napoleon was broke and needed some quick dough -
In 1831, British scientist Michael Faraday discovered electromagnetic induction, demonstrating that a changing magnetic field can induce an electric current. This discovery was pivotal for the development of electric motors, generators, and modern electromagnetic theory. Faraday's work also extended to electrochemistry, laying the groundwork for later advances in both fields. -
In 1886, German physicist Eugen Goldstein discovered canal rays, which are positively charged ions. This discovery led to the identification of the proton, a crucial step in understanding atomic structure. Goldstein’s work on cathode ray tubes revealed that atoms also contain positively charged particles, complementing the discoveries of electrons made by J.J. Thomson. -
Great step forward toward a cleaner tomorrow. -
In 1897, British physicist J.J. Thomson discovered the electron through experiments with cathode rays, showing that atoms are not indivisible but contain smaller particles. This discovery revolutionized the understanding of atomic structure and led to the development of the first subatomic model of the atom, the "plum pudding" model, in which electrons are embedded in a positively charged "soup." -
First Proposed: 1904
Superseded By: Rutherford’s Nuclear Model
Change Date: 1911
The discovery of the electron by J.J. Thomson in 1897, the understanding of atoms changed, leading to the introduction of the Plum Pudding Model, which proposed that atoms contained smaller subatomic particles (electrons) embedded in a positively charged "pudding." -
In 1909, American physicist Robert Millikan performed his famous oil drop experiment, which allowed him to measure the charge of the electron. This precise measurement helped determine the electron's mass and provided key evidence for the understanding of atomic structure. Millikan's work in electromagnetism and his discovery of the electron's charge were critical in advancing the field of quantum mechanics. -
In 1911, New Zealand-born physicist Ernest Rutherford conducted his famous gold foil experiment, through which he discovered the atomic nucleus. By observing how alpha particles scattered when directed at a thin sheet of gold, Rutherford concluded that atoms have a small, dense, positively charged nucleus at their center, fundamentally changing the understanding of atomic structure. -
First Proposed: 1911
Superseded By: Bohr’s Solar System Model
Change Date: 1913
Info: Rutherford’s model positioned electrons around the nucleus but didn’t explain why electrons didn’t spiral inward due to their charge. In 1913, Niels Bohr proposed the Solar System Model, suggesting that electrons orbit the nucleus in fixed, quantized energy levels, similar to planets orbiting the sun. This model explained the stability of atoms and the spectral lines of hydrogen. -
In 1913, Danish physicist Niels Bohr proposed the Bohr model of the atom, where electrons orbit the nucleus in discrete energy levels. This model explained the spectral lines of hydrogen and incorporated quantum theory, suggesting that energy levels are quantized. Bohr's model was a major advancement in understanding atomic behavior and laid the foundation for later quantum mechanics. -
First Proposed: 1913
Superseded By: Electron Cloud (Wave Mechanical) Model
Change Date: 1926
Info: Although Bohr’s model worked well for hydrogen, it failed for atoms with more than one electron. By 1926, Erwin Schrödinger and others developed quantum mechanics, leading to the Electron Cloud Model. This model viewed electrons as existing in probabilistic clouds, with their exact positions unknown, described by wave functions rather than fixed orbits. -
The first of the world wars millions perish to pointless monarchs disputing -
One of the worst epidemics since the bubonic plague 20x worse than covid-19 -
In 1926, Austrian physicist Erwin Schrödinger formulated the Schrödinger equation, a fundamental equation in quantum mechanics that describes the wave-like behavior of particles, such as electrons. His work provided a mathematical framework for understanding the behavior of atoms and molecules at the quantum level, and his famous thought experiment, "Schrödinger’s cat," illustrated quantum superposition. -
In 1927, German physicist Werner Heisenberg formulated the uncertainty principle, which states that it is impossible to simultaneously measure both the exact position and momentum of a particle with absolute precision. This principle became a cornerstone of quantum mechanics, highlighting the limits of measurement at microscopic scales and challenging classical physics’ assumptions about determinism. -
First Proposed: 1926 (Schrödinger’s wave equation)
Superseded By: Electron Cloud Model with Neutrons
Change Date: 1932
Info: The Electron Cloud Model was further refined after James Chadwick’s discovery of the neutron in 1932. Before this, the atom was thought to consist only of protons and electrons, but the neutron added a neutral particle to the nucleus, helping to explain atomic mass and leading to a more complete understanding of isotopes and atomic structure. -
In 1932, British physicist James Chadwick discovered the neutron, a neutral subatomic particle found in the nucleus of atoms. This discovery completed the understanding of atomic structure by revealing that the nucleus is made up of protons and neutrons, explaining atomic mass and enabling further developments in nuclear physics, including the development of nuclear energy and weapons. -
The same as the electron cloud model except the nucleus has protons and neutrons. -
Man harnesses the true power of the atom and WW2 ends faster than it came. The world will never be the same.