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460
Democritus- Atomic Theory
Proposed Atomic Theory: states that all atoms are small, hard, indivisible and indestructible particles made of a single material formed into different shapes and sizes and without democritus' propsed theory, many others wouldnt have differed, which would have led to a much different approach to the atom and maybe many other things wouldnt have been discovered. Democritus was the start to the research of the atom. -
Period: 460 to
The Atom Through History
An atom is the smallest particle of an element that retains all the properties of that element; is eletrically neutral, spherically shaped, and composed of electrons, protons, and neutrons. -
Antoine Lavoisier - “The Father of Modern Chemistry”
First person to generate a list of thirty-three elements in his textbook, identifying Hydrogen and Oxygen, said that combustion occurs when oxygen combines with other elements, Also came up with the Law of Conservation of Mass which states, in a chemical reaction, matter is neither created nor destroyed which is why he made such an important impact on science. He also defined the term "elements" as substances that have definite chemical properties. -
Jospeh Proust- Law of constant Composition
(Stoichiometry) He proposed that a given compound always contains the same elements in the same proportions by mass- Law of Definite Proportions: no matter how a compound is made, or the amount, the reactants would always join the same. This whole proposed discovery led John Dalton to come up with his theory, which as we know, was a big impact. -
Dalton- Atomic Theory
Based on the fact different elements could be distinguished by differences in their weights.This theory proposed that:
1)all matter is composed of atoms
2)atoms cant be created/destroyed
3)atoms of the same element are identical
4)different elements have different types of atoms
5)chemical reactions occur when atoms are rearranged
6)Compounds are formed from atoms of the constituent elements
Daltons theory gave logical evidence for this concept and led the way into new fields of experimentation. -
J.J Thomson- Plum Pudding
Proved that atoms can be divided into smaller parts and that an atom is neutral; Using cathode-ray tube he discovered electrons; In 1897, proposed the Plum Pudding Model which states that atoms mostly consist of positively charged material with negatively charged particles located throughout the positive stuff. This event is important because Thomson discovered the electron, which is one of the more important things an atom can have. -
Marie Curie- Radioactivity- *Minority
"Mother of Modern Physics"- radioactivity(unstable atoms); Discovered and isolated polonium and radium, and established the nature of radiation and beta rays which also brought us to new medicines in treating cancer. she was a pioneer in the field of radiology. -
Hantaro Nagaoka- *Minority
Nagaoka rejected Thomson's model on the idea that opposite charges are impermeable. He proposed a model in where a positively charged center is surrounded by a bunch of revolving electrons, like the rings of saturn. He was important becuase he decided to reject thomson's big new theory and he was one of the first scientist's to present a saturnian model of the atom -
Ernest Rutherford- The Atomic Theory
the atom has a central positive nucleus surrounded by negative orbiting electrons. This model suggested that most of the mass of the atom was contained in the nucleus, and that the rest of the atom was mostly empty space.
“Father of Nuclear Physics” - did lots of work on radioactivity: alpha/beta particles, gamma rays/waves.
He figured out what atoms pretty much consisted of on the inside and how it things move in there and he discovered the nucleus. -
Niels Bohr- Bohr model
Bohr Model- electrons travel around the nucleus of an atom in orbits or definite paths. The electrons can jump from a path in one level to another path( emits light). The farther away the electrons get from the nucleus, the more the paths can hold. This is what distinguishes the atoms chemical properties. Rutherford's student brings us the idea that electrons travel in orbits around the atom's nucleus. -
James Chadwick- Neutrons
Discovered the neutrons! he named it the neutron because he noticed that there was no electrical charge and it accounted for the missing weight within the nucleus and the neutron completed the atom and made it a whole. He completed the missing piece to the ato puzzle! -
Rosalind Franklin- *Minority
Made important discoveries about the molecular structure of coal and carbon, which were later used to develop strong carbon fibers and to slow reactions in nuclear power plants;First to discover the structure of DNA; x-ray crystallography- images allow viewer to figure out how the atoms are arranged so we could investigate them, in a closer manor. Allowing us to see atoms in a physical way. -
Maria Goeppert-Mayer- *Minority
developed the nuclear shell model of atomic nuclei, an achievement honored when she became the third woman ever awarded the Nobel Prize for physics.
In the nuclear shell model, we learn why certain numbers of nucleons in the nucleus of an atom cause an atom to be extremely stable. Important woman in phyisics.
