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430 BCE
Democritus
Democritus came up with one of the earliest theories/designs of the atom. He theorized that atoms were small, hard, uniform, and built up all matter. He also gave them an early version of their name that likely changed into the word “atom” over time. -
500
Alchemists
Alchemists discovered many elements and came up with many experimental concepts in chemistry that went on to broaden our understanding of atoms and their structures. -
Antoine Lavoisier
Antoine Lavoisier created the law of conservation of mass, an incredibly important law in the understanding of chemical reactions. He also was one of the first people to isolate oxygen gas and name it. -
Law of Conservation of Mass
The law of conservation of mass, invented by Antoine Lavoisier, changed our understanding of atoms and their roles in chemical reactions. -
Law of Definite Proportions
The law of definite proportions is an important part of our understanding of the atoms in chemical compounds. Its discovery helped us gain a greater understanding of how atoms make up various compounds. -
Joseph Louis Proust
Proust’s law of definite proportions was important in our understanding of atoms’ role in chemical reactions. -
Dalton's Atomic Theory
Dalton’s atomic theory was a mostly accurate theory on the behavior and structure of atoms. Aside from a few more recent discoveries, it is almost completely accurate to our current knowledge of atoms. -
John Dalton
Dalton’s atomic theory was relatively accurate to the modern day properties of atoms and his theory is still sometimes used to describe atoms early on. His billiard-ball model was an important building block in our understanding of the structure of atoms. -
Dmitri Mendeleev
Dmitri Mendeleev’s periodic table was important in our understanding of atomic structure. An updated version of his model of the elements is still used to this day. -
Cathode Ray Tubes
J.J. Thomson’s discovery of the electron using cathode ray tubes changed the worldview on the structure of atoms. -
Plum Pudding Atomic Model
J.J. Thomson’s model of the atom was one of the first to include electrons as a source of a negative charge. This was revolutionary for models of atomic structure and helped broaden our understanding of atoms greatly. -
J.J. Thomson
J.J. Thomson discovered the electron, thus completely changing the world’s view of the structure of an atom. His plum pudding model was the first to include the electron as a source of a negative charge. -
Oil Drop Experiment
The oil drop experiment broadened our understanding of the electrons in atoms. A better understanding of their charge allowed us to better understand their movement and positioning. -
Robert Millikan
Robert Millikan discovered the charge of an electron. This was incredibly important in our understanding of the structure of an atom. -
Gold Foil Experiment
The gold foil experiment helped change our understanding of the position of matter in the atom. The discoveries made completely changed the model of an atom’s structure. -
Ernest Rutherford
Ernest Rutherford discovered that atoms were mostly empty with their mass being centered in the nucleus. This completely shifted models of atomic structure from being large and bulky to being centered around the nucleus like we know they are today. Rutherford also created a revolutionary model of the atom called the nuclear model which was used for many years prior to the creation of the Bohr and quantum mechanical models. -
Nuclear Model
Ernest Rutherford’s nuclear model was the first to suggest that elements were dictated by the charge of their nucleus rather than by their mass. It was also the first model to include a nucleus. Overall, the nuclear model was revolutionary for our knowledge of atomic structure. -
Henry Moseley
Moseley’s discovery related to atomic numbers and their corresponding frequencies on lines of the x-ray spectra became known as Moseley’s law and greatly furthered the world’s understanding of the atom. -
Niels Bohr
Niels Bohr’s research into electron orbits helped him create an updated model of the atom which included almost every part of an atom's structure correctly. The Bohr model is still even used today due to its simplistic approach to atomic structure. -
Planetary Model
The Bohr model, or planetary model, was the first to discuss the specifics of electron orbits and despite its few minor inaccuracies, it’s still often used today to explain atomic structure. -
Erwin Schrodinger
Schrodinger’s theories on quantum wave mechanics that helped us better visualize the movement of particles inside models of atomic structure. Schrodinger’s model of the atom is one of the most accurate models to date. -
Quantum Mechanical Model
Erwin Schrodinger’s quantum mechanical model of the atom is one of the most accurate atomic structure models to date. It accurately portrays the behavior of electrons in the electron clouds through the use of orbitals. -
Werner Heisenberg
Werner Heisenberg created an important model on the interaction between protons and neutrons that advanced the world’s understanding of atoms. -
James Chadwick
James Chadwick’s discovery of the neutron changed the world’s understanding of atomic structure. Prior scientists had theorized that there were other parts of an atom besides the protons and electrons, but Chadwick was the first to prove it.