Development of the Atomic Theory Rafael Angulo

Plato

427 BCE

Plato theorized that solid forms of matter are made of indivisible elements that are triangular, rather than circular in 427 BCE. Helped lead to the discover of the shape of the atom.

Democritus

400 BCE

Democritus introduced the idea that there are tiny particles, or atoms, that are the basic building blocks of all matter in 400 BCE. This helped introduce the idea that there is a simple particle that is the smallest unit you split something into eventually.

The Alchemists

522

The Alchemists started to involve themselves in Aristotle's atomic theory starting in 522 CE, two centuries after Aristotle's death. They also studied natural processes and tried to turn common objects into gold, which led to the discovery of the atom. They helped lead to scientists being able to prove that elements are the basic building blocks of matter.

Robert Boyle

1660

Robert Boyle contributed to atomic theory by demonstrating that all matter is made up of tiny particles he called corpuscles, or atoms. Boyle defined elements as matter that can't be broken into simpler substances in 1660, which helped the advancement of the atomic theory by making the atom the smallest unit reachable.

Antoine Lavoiser

1789

Antoine Lavoisier discovered that mass is neither destroyed or created in chemical reactions in 1789. This helps advance the atomic theory by defining that mass made of atoms which is everything, isn't created or destroyed in in chemical reactions.

Billiard Ball Atom Model

1802

John Dalton developed the Billiard Ball Atom Model around the early 1800's in which there are electrons in in different orbits around a nucleus with protons and neutron. This advanced the atomic theory by allowing a basic idea of what an atom may look like to be seen by people and influence what they might think about the atom.

John Dalton

1803

John Dalton suggested that all matter was made of indivisible and indestructible atoms that each have a distinct mass and property, that correlate to a specific element in 1803. This advanced the atomic theory by defining that elements have distinct masses and properties, which can be sorted on the periodic table.

Amadeo Avogrado

1811

Amadeo Avogrado worked on the discovery of the gas law, later known as Avogrado's law. In 1811 his hypothesis states that at the same temperature and pressure that equal ammounts of different gasses contain an equal ammount of particles. This advanced the atomic theory by saying that in a certain state of matter and atmosphere, different elements will have the same ammount of particles.

Dmitri Mendeleev

1869

Dmitri Mendeleev crated the framework for the modern periodic table. He arranged elements according to atomic weight and put elements that didn't fit in a different order. This lead to the creation of the periodic table later on, which proved how each element has certain properties in which they can be sorted.

JJ Thompson

1897

JJ Thompson experimented with cathode ray tubes and found that all atoms contain tiny, negatively charged subatomic particles, known as electrons in 1897. Thompson also proposed the "Plum Pudding" model of the atom with electrons in a positively charged "matter soup" in 1904. This helped explain the structure of an atom in a way he thought was appropriate.

Pierre and Marie Curie

1898

Pierre and Marie Curies discovered the radioactive elements of radium and polonium that occur in uranium in 1898. They also found out that radioactivity is the emission of ionizing rays by certain types of atoms. They helped the atomic theory by discovering two elements that had radioactive properties that have slightly different properties than normal atoms.

Plum Pudding Atom Model

1904

JJ Thompson developed the Plum Pudding Atom Model in which there are electrons floating around in a "soup" of positive matter in 1904.This helped advance the atomic theory by putting a second perspective on an atom's structure.

Albert Einstein

1905

Albert Einstein mathematically proved the existence of atoms and said that all liquids are made up of molecules in 1905. This helped with to the atomic theory, because as atoms were now mathematically proven, there was a path to find the true structure of atoms.

Robert Millikan

1910

Robert Millikan found an accurate determination of an electron's charge using the "fail-drop" method using oil and that quantity was a constant for electrons in 1910. This helped the atomic theory by defining that electrons had a specific charge.

Ernest Rutherford

1911

Ernest Rutherford of New Zealand described the atom to have a tiny, dense, and positively charged core, or nucleus in 1911. He also described that the mass of the atom is concentrated in the nucleus and negatively charged electrons circulate around it.

Neils Bohr

1913

The Danish physicist Neils Bohr developed an atom model with a nucleus including protons and electrons revolving in orbit around the center in 1913. He contributed to the atomic theory, because he put foward a refined model of the atom with protons and electrons.

Solar System Atom Model

1913

Niels Bohr developed the Solar System Atom Model in 1913 in which the electrons are in orbit in a circular way like planets around a center with protons and neutrons.

Henry G. J Mosely

1913

Henry G. J Mosely arranged the elements in a periodic table according to atomic number in 1913. Also, he realized that atoms identities are based on the number of protons they have, and protons represent the atomic number for elements. This helped the atomic theory by organizing the elements with their masses and properties.

Electron Cloud Atom Model

1926

Erwin Schrodinger and Werner Heisenberg developed the Electron Cloud model with the protons and neutrons in the center with a "cloud" of electrons surrounding it in 1926.

Erwin Schrodinger

1926

Erwin Schrodinger created a powerful model of the atom in 1926. He combined the behavioral equations for waves with the "de Broglie" equation to make a mathematical model for the atomic electron distribution. This helped the atomic theory by helping determine where electrons were in an atom.

Werner Heisenberg

1927

Werner Heisenberg formed a type of quantum mechanics based on sets of number in a rectangular array in 1925. But in 1927, Heisenberg proposed an uncertainty relation that set a cap on the precision of the position and velocity of a particle being determined which helped scientists try to find out where the different subatomic particles were. This helped the atomic theory by saying that electrons couldn't be located to a exact point.

James Chadwick

1932

James Chadwick found that in the core, or center of a nucleus has an uncharged particle known as a neutron in May 1932. This is important because there were now three different subatomic particles in an atom. This advanced the atomic theory by saying that an atom had three different particles, each with a different ammount of electric charge.