-
400
Democritus "discovers" the atom
The Greek philosopher Democritus came up with the first ever theory about the atom. His theory went like so:
Matter could not be divided into smaller and smaller pieces forever, eventually the smallest piece would be obtained. This piece would be indivisible.
He named the smallest piece of matter 'atomos,' meaning 'not to be cut'. -
Period: 400 to
History of the Atom
Dating back from Democritus' theory right up to Neils Bohr in the early 20th Century. -
Isaac Newton's Theory
In 1704, Newton theorised a mechanical universe with small, solid masses in motion. -
John Dalton's Atomic Theory
In the mid 18th Century, the English scientist John Dalton proposed that all matter is made of atoms and that atoms are indestructible and indivisible. He also proposed that compounds are formed by a combination of two or more different kinds of atoms. -
Dimitri Mendeleev Periodic Table
In 1869, Dimitri Mendeleev created the periodic table of the elemts. -
G. J Stoney (Electrons)
In 1874, the Anglo-Irish physicist G.J Stoney theorised that electricity was comprised of negative particles that he called electrons. -
Thomson's Theory
In 1897, Joseph John Thomson proposed that an atom consists of a positive chargd, with negatively charged electrons embedded in it. -
Max Planck Theory of Light
In 1900, the German physicist Max Planck proposed the idea of quantitization to explain how a hot, glowing object emitted light. 18 years later, he won the Nobel Prize in Physics. Together, Planck and Einstein constituted the fundamental theories of 20th Centruy physics. -
Hantaro Nagaoka (Structure of the Atom)
In 1903 the Japanese physicist, Hantaro Nagaoka proposed an atomic model called the Saturnian model, which described the structure of an atom. Nagaoka opposed Thomson's model of the atom, and instead made one which resembles Saturn and it's rings, with a positively charged center surrounded by revolving electrons. -
Rutherford's Atomic Theory
Structure of the Atom: Ernest Rutherford
On the 7th March 1911, Ernest Rutherford presented a paper to the Manchester Library accurately describing the structure of an atom. Due to an experiment he performed, he found that an atom had almost all its mass concentrated at the center, in a nucleus, with the vast majority of it being empty space. -
H.G.J Moseley (Element Number)
In 1914, the English physicist H.G.J Moseley discovered that the number of protons in an element determines its atomic number. This theory was the first experimental evidence that supported Bohr's theory. -
Neils Bohr's Theory
In 1922, Bohr refined Rutherford's atomic model, now saying that electrons;
Orbit the nucleus without losing energy.
Could move only in fixed orbits of specific energies.
With lower energy would orbit closer to the nucleus, whereas those with a higher energy would orbit further from the nucleus. -
Paul Dirac
In the early 20th Century, the English theoretical physicist, Paul Dirac, proposed the existence of anti-particles. Due to his autism, he was considered quite unusual and odd by his friends and colleagues, yet had many meetings with Einstein who said to him, "This balancing on the dizzying path between genius and madness is awful." This quote was said in relation to his high level of autism. -
Enrico Fermi (The Nuclear Reactor)
Two years after the Second World War, the Italian theoretical and experimental physicist, Enrico Fermi created the first ever man-made nuclear reactor. This was a massive leap for technology and has created a path for so many more inventions throughout the decades. After the ignition of the Soviet's first ever WOMD, Fermi strongly opposed the GACAEC (General Advisory Committee of the Atomic Energy Commission). He opposed them on moral and technical grounds.
