-
460 BCE
Democritus
Democritus, theorized that atoms were
specific to the material which they composed.
In addition, Democritus believed that the atoms
differed in size and shape, were in constant
motion in a void, collided with each other. -
Period: 460 BCE to
history of the atom
-
Antoine Lavoisier
Antoine Lavoisier (1743-1794) was the first person to make good use
of the balance. He was an excellent experimenter. He proposed the
Combustion Theory which was based on sound mass measurements. -
John Dalton
Experiments with gases that first became
possible at the turn of the nineteenth century
led John Dalton in 1803 to propose a modern
theory of the atom based on the following
assumptions. 1. Matter is made up of atoms
that are indivisible and indestructible. -
J. J. Thompson
In 1897, J.J. Thomson discovered the electron
by experimenting with a Crookes, or cathode ray
, tube. He demonstrated that cathode rays were
negatively charged. In addition, he also studied
positively charged particles in neon gas. -
Marie Curie
And Marie was proven right: in 1898 the Curies
discovered two new radioactive elements: radium
(named after the Latin word for ray) and polonium
(named after Marie's home country, Poland) -
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. -
Albert Einstein
In 1915, Einstein published the general theory of
relativity, which he considered his masterwork.
This theory found that gravity, as well as motion,
can affect time and space. -
Max Planck
Planck performed the only experiments of his
scientific career, studying the diffusion of hydrogen
through heated platinum, but transferred to
theoretical physics. -
Niels Bohr
Bohr was working for the Nobel laureate
J.J. Thompson in England when he was introduced
to Ernest Rutherford, whose discovery of the
nucleus and development of an atomic model. -
Robert Millikan
His oil drop experiment helped to quantify the
charge of an electron, which contributed greatly
to our understanding of the structure of the atom
and atomic theory. -
Werner Hiesenberg
His new theory was based only on what can be
observed, that is to say, on the radiation emitted by
the atom. -
Erwin Schrodinger
Schrödinger used mathematical equations to
describe the likelihood of finding an electron in a
certain position. This atomic model is known as the
quantum mechanical model of the atom. -
James Chadwick
Soon realized that the newly discovered neutron,
as an uncharged but fairly massive particle, could
be used to probe other nuclei. -
Louis De Broglie
Louis inherited the title of duke. Maurice, who was
also a physicist and made notable contributions to
the experimental study of the atomic nucleus,
kept a well-equipped laboratory