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460
Democritus
In 460 BC, Democritus came up with the idea of an atom. What happened, he wondered, when you continued to break a material in half over and over? How small could it get? Eventually he came up with the idea of an atom; a the smallest part of a substance. -
Newton
In 1704 Isaac Newton suggested that maybe there were small particles moving around in space that couldn’t be seen by the human eye. This proposal opened up scientist’s to the idea of atoms, and it probably inspired future scientists. -
Dalton
In 1803, Dalton first wrote an entry in his logbook called "Observations on the Ultimate Particles of Bodies and their Combinations." After he figured out the existence of atoms, he made a table with around 36 symbols that were arranged by their atomic masses. -
Dalton 2
In 1805, Dalton published five points of his atomic theory:
1. Matter is made up of atoms
2. Atoms of the same elements have the same characteristics, including mass.
3. Atoms are unable to divide, form, or destroy.
4. Atoms from different types of elements come together with simple whole-number ratios to make new compounds.
5. Atoms are reorganized, combined, and separated. -
Plucker
Plucker invented the Cathode Ray Tubes, which revolutionized the study of atoms. The cathode ray tube is an incredibley useful tool for all scientists after him who studied atoms. -
Mendeleev
Mendeleev made up a periodic table in 1869. He organized the elements by atomic mass, but he also organized them so there would be similar properties among the elements in each columns and left space for different undiscovered elements. -
Crookes
Sir Crookes did a lot in the name of science. Not only did he discover a new element, he also found out a lot about cathode rays. He was able to display proof and confirm information proposed by other scientists. He became a knight -
Thomson
Thomson discovered the electron while experimenting with cathode rays. Before him other scientists had suggested the existence of more particles in the atom, but Thomson was the one who experimented to find it. -
Soddy
At the turn of the century, Soddy discovered isotopes, which are different versions of one type of atom, but they are made of the same amount of everything. This discovery was crucial in understanding the inner workings of atoms all around us.He eventually won a Nobel Prize for this work. -
Nagaoka
Nagaoka proposed another atomic theory, which said that atoms had big nuclei and electrons that went around the nucleus. This model was called the Saturnian model, and it was a planetary model -
Millikan
Millikan's Oil Drop Experiment gave away massive clues about atoms; the charge of electrons. Using the experiment pictured he was able to deduce the charge, and he went on to win a Nobel Prize for this amazing work. -
Bohr
Bohr figured out that atoms move around in stationary orbits, which helped him discover various other relationships between the different parts of an atom. -
Moseley
Moseley figured out that the atomic number reveals how many protons there are in the nucleus. Moseley also figured out more things about the atomic structure, which propelled science further. Sadly, he died in 1916 and could no longer contribute to the wealth of knowledge he had shared with the world. -
Chadwick
After reviewing Rutherford's discovery, Chadwick realized that there were more particles in the nucleus because the atomic mass was less than the atomic number. Rutherford suggested the existence of the neutron, but he didn’t have evidence. Eventually, after looking at other scientist’s experiments, Chadwick did his own and found proof of the neutrons.
