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476 BCE
Medieval Alchemy
This had been a combination of science, philosophy, and mysticism. Alchemists had held their secrets closely with a system of characters and symbols to represent the materials they studied. -
476 BCE
'Turning Lead to Gold'
During the period of Medieval Alchemy, alchemists had strongly believed that the change from one substance to another was something that could be done. Hence the term "turning iron into gold". -
476 BCE
Achievments of Medieval Alchemy
Alchemists had been able to produce hydrochloric acid, nitric acid, potash, and sodium carbonate. In a summary, the alchemists during the Medieval period had molded the foundation for chemistry, as they identified elements such as bismuth, and arsenic. -
476 BCE
Alchemy of Medieval Time
The heart of this all had been the idea that all matter was made entirely of the four main earthly elements; those being earth, water, air and fire. It had been theorized that any substance on earth could be formed using the correct combination of those four elements. -
460 BCE
Democritus' Atomic Theory
- All matter is made up of invisible particles called atoms
- Atoms cannot be destroyed
- Atoms are solid yet invisible
- Atoms are homogeneous
- Atoms differ in size, shape, weight, arrangement and position
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460 BCE
Democritus' Atomic Theory
Democritus was a student of the philosopher Leucippus, who had first brought forward the atomic theory. He had believed that if a solid were to be continuously cut, it would eventually become so many particles so small they were no longer able to be cut. However, those pieces would still be there, just not seen with the naked eye. -
460 BCE
Atomos
Democritus' theory had stated that “The universe is composed of two elements: the atoms and the void in which they exist and move.” He believed that atoms were tiny quantities of matter. He created the name of "atom" from the root Greek word "atomos". It meant "uncuttable". -
Period: 460 BCE to 370 BCE
Democritus
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John Dalton
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John Dalton's Contribution
This great man was a chemist, physicist, and meteorologist. He had also been a specialist on colour blindness. His theory on colour blindness had been one of the first idealisms published. The other very poignant moment which makes this man stand out is his work in developing the modern atomic theory. -
Dalton's Law
This is also known as Dalton's Law of partial pressure. It states that within a combination of non reacting gases, the total pressure extracted is equal to the sum of the fragmentary pressures of individual gases. -
Dalton's Theory
Dalton had stated that the atom formed elements, and that assortments of elements would have differently sized and weighed atoms. He conducted experiments which he concluded from that the range of vapor pressure for every liquid was the same, for the equivalent range of temperatures. -
Dalton's Atomic Theory
He stated that all elements were made of atoms, that the same elements had the same identity, and that compounds were formed by connecting atoms in a specific ratio. His theory had also concluded that atoms retained their physique during chemical reactions. -
Dalton's Atomic Theory
Experiments involving materials in the state of gas led Dalton to propose a theory on the premise that all matter is made of atoms that are invisible and indestructible.In writing, he had conducted experiments which he concluded from that the range of vapor pressure for every liquid was the same, for the equivalent range of temperatures. -
Dalton's Atomic Theory
He believed that all atoms were unique, and that they could not be created nor destroyed by chemical processes. Dalton created the law of multiple proportions, which stated that elements combine at the atomic level in standard ratios, which then differ depending on those compounds being fused, weighted to their atomic mass. He proposed that every element was composed of atoms in a unique variety, and despite the inability to alter them, they could be combined to create complex structures. -
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Antoine Henri Becquerel
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J.J Thomson
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Pierre Currie
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Marie Curie
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Ernest Rutherford
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Neil Bohr
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James Chadwick
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X-Rays
Henri Becquerel used fluorescent minerals to study x-rays, after conducting an experiment he believed the aforementioned uranium absorbed the suns energy, and were emitted as x-rays.The sample he left to be unexposed had fogged. Since the images he produced were strong, this proved that the uranium emitted radiation without a reliance on external sources of energy. -
Radioactivity
Henri Becquerel stated that the emissions released during his experiment could not have been x-rays. Rays from the radiation were being bent by the magnetic field. Different radioactive substances had been put through the field and were deflected in altering directions. -
Uranium Salts
The newly discovered x-rays led to Becquerels studies on how uranium salts were affected by lights. He left the salts on a photographic plate which left an image behind, with no use of external energy sources. Accidentally, he learned that these salts were emitting radiation which were recorded on a photographic plate. This led to his discovery of radioactivity -
The First Atom to Be Discovered
The key stepping stone of the atomic theory was the plausibility that atoms are not the smallest existing elements. J. J Thomson discovered the electron, a subatomic particle with a negative charge, in 1897. This led to his creation of a "plum pudding model" for the atom. This was through his exploration of cathode rays, which he learned could work it's way through the air on a larger extended length than expected for such tiny particles. -
Discovery of the Electron
In 1897, J.J Thomson had conducted the unraveling of the mystery of the atom. It was exhibited that an atom could be split into even smaller parts. He recognized that the atom was neutrally charged, however had only discovered the negatively charged electron that were much more compact in comparison to the whole atom. His plum pudding model represented his idea that the electrons were encased and scattered like 'raisins in plum pudding' within a positively charged sphere of matter. -
Marie and Pierre Curie
This married couple of ingeniousness are best remembered for their work on radioactivity. They led the discovery of Radium and Polonium. -
The Curie's
Marie Curie was a prize winning physicist and chemist. Along with her husband, they had theorized that the radioactive particles had caused for atoms to break down, and released radiation in the forms of both energy and subatomic particles. -
Radiation
Using Becquerel's discoveries, the Curie's proved that the uranium atoms had emitted rays that were fogging the plate. These rays and particles given off by the radioactive substances were known as radiation. They discovered the radioactivity was in correlation to the volume of radioactive material. -
Ernest Rutherford the Experimentalist
This man had made incredible discoveries in radioactivity and nuclear physics, uncovering information behind alpha and beta rays, and setting laws for radioactive decay. He is known as the father of nuclear chemistry and nuclear physics. -
Rutherford's Gold Foil Experiment
During his studies, he formulated the Gold Foil experiment alongside Hans Geiger and Ernest Marsden. They would point a stream of alpha particles at foils of metal and measured the scatter with a fluorescent screen. He concluded that atoms were more than just empty space and electrons, and that atoms had positively charged centers which contained most of their mass. This led to the theory of atomic structure. -
Ernest Ruthorford
He concluded from his experiment that atoms were more than just empty space and electrons, and that atoms had positively charged centers which contained most of their mass. -
The Danish Physicist, Niels Bohr
Bohr made extensive contributions to the comprehensions of the atomic structure and quantum theory. His best tribute to modern physics had been the atomic model. He had also consolidated the Planck quantum theory, which stated "When electrons change orbits, they emit a quantum of discrete energy.". -
Bohr Model
The Bohr model shows the number of electrons and their location relevant to the nucleus, as they orbited. -
Bohr Atomic Model
He discovered that the electrons traveled in orbits around the nucleus, with the number of electrons per orbit determining the chemical properties of the elements. He stated that the electrons could exist only at specific distances from the nucleus. -
The Proton
Rutherford had been credited as well for the discovery of the proton in 1919, after conducting an experiment leading to the "splitting" of an atom in a nuclear reaction where he inundated nitrogen with alpha particles from radioactive material. He observed the proton released higher energy than the alpha particles. -
James Chadwick
Sir James Chadwick was a physicist best recognized for his discovery of the neutron. His research was largely focused towards radioactivity. Through extensive studies, they saw that the atomic number was less than that of the atomic mass. Electrons have close to no mass, he believed there had to have been something else there other than just protons and electrons. -
Finding The Neutron
Rutherford put the idea out there that there could have been a particle with mass but no charge, he then called it a neutron and envisioned it as a proton and electron paired together. Chadwick continued experimenting in search for neutral particles. -
Success of The Neutron
His experiments were deemed successful, and Chadwick was able to establish that the neutron did in fact exist with a mass 0.1% higher than that of a proton by bombarding alpha particles to boron and analyzing those interactions between the interaction of nitrogen with neutral particles.
