-
460 BCE
Democritus
He thought that atoms were tiny, uncuttable, and solid particles that were surrounded by empty space. He also introduced the idea of the atom as the building blocks of matter. -
427 BCE
Plato
Plato theorized that solid forms of matter are composed of elements shaped like triangles. Plato also argued that atoms are indivisible not the matter they come together to create. -
500
The Alchemists
Created experiments with the idea of matter. They also believed that all metals were formed from mercury and sulfur. -
Robert Boyle
He showed that matter is made of tiny particles. He named these tiny particles "corpsucles" which are known now as atoms. -
Antoine Lavoisier
He helped define the law of conservation of mass. He said that matter was made of atoms that were not created or destroyed during a chemical reaction. -
Billiard Ball Model
Dalton made a model of an atom that looked like a billiard ball. -
John Dalton
His theory says that all matter is made of atoms that are invisible. He also claimed that all elements had their own kind of atom. -
Amedeo Avogadro
He said that elementary gases such as hydrogen, oxygen, and nitrogen, were made of only two atoms. He was also the first scientist to propose that elements could exist as molecules instead of individual atoms. -
Dmitri Mendeleev
He devised the periodic classification of the chemical elements in which they were arranged by atomic weight. He lived during the same time as Louis Pasteur, and Marie Curie. -
JJ Thomson
His experiments showed that all atoms have tiny negatively charged subatomic particles now known as electrons. He was also an amateur botanist. -
Pierre and Marie Curie
Marie suggested that the energy two elements they were studying gave off were particles from small atoms in the elements that were disintegrating. Both Pierre and Marie were awarded the Davy Medal of the Royal Society of London in 1903. -
Plum Pudding Model
J.J Thomson created this model in 1904. -
Albert Einstein
He mathematically proved the existence of atoms. He also realized that these molecules would fluctuate statistically. -
Robert Millikan
He successfully determined the magnitude of an electrons charge. To prove this he did multiple experiments with oil and two metal plates. -
Ernest Rutherford
He described the atom as having a tiny, dense, and positively charged core called the nucleus. The element names Rutherfordium was named in his honor. -
Neils Bohr
He proposed a theory for hydrogen atoms in which electrons move around the nucleus but only in prescribed orbits. -
Henry G. J. Mosely
He created his law which states that the square root of the frequency of the x-ray emitted by an atom is proportional to the atoms atomic number. He also predicted the existence of four new elements which were later discovered. -
Solar System Model
Otherwise known as the "Bohr Model" the solar system model shows atoms as appearing as a mini solar system. -
Electron Cloud Model
Erwin Schrodinger and Werner Heisenberg created the electron cloud model. -
James Chadwick
He discovered the neutron and was able to measure its mass. In 1935 he was awarded the Nobel Prize for Physics.