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456 BCE
Democritus
Democritus hypothesized that atoms cannot be destroyed, differ in size, shape and temperature, are always moving, and are invisible. He believed that there are an infinite number of atoms. This hypothesis was created in 465BC. -
John Dalton
John Dalton identified the hereditary nature of red-green color blindness. In 1803 he revealed the concept of Dalton’s Law of Partial Pressures. Also in the 1800s, he was the first scientist to explain the behavior of atoms in terms of the measurement of weight.
In the early 1800s, Dalton also postulated a law of thermal expansion -
Niels Bohr
He developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level (or orbit) to another.
Won the 1922 Nobel Prize in physics for his ideas, and in the late 1930s, contributed to the liquid droplet theory -
J.J Thompson
Thomson won the 1906 Nobel Prize in Physics
In 1912, he discovered that neon was composed of two different kinds of atoms, and proved the existence of isotopes in a stable element.
He discovered that the ratio was the same regardless of what type of gas was used, which led him to conclude that the particles that made up the gases were universal.in 1894 -
Ernest Rutherford
In 1911, he was the first to discover that atoms have a small charged nucleus surrounded by largely empty space, and are circled by tiny electrons, which became known as the Rutherford model (or planetary model) of the atom.
He was dubbed the “Father of the Nuclear Age”. Rutherford received the Nobel Prize for Chemistry in 1908
