The be created or destroyed. In the late 1800’s

The
origin of the word “atom” comes from the greek word “atomos” which means
uncuttable or indivisible. The atomic theory was first founded in around 460
BC, although some thought it was 490 BC by Democritus who was an Ancient Greek
pre-Socratic philosopher primarily remembered today for his formulation of an
atomic theory of the universe. His mentor, Leucippus, originally came up with
the atomic theory, but it was then adopted by Democritus.

Around
the same time as Democritus there was another Ancient Greek philosopher named
Aristotle who believed that all materials on earth are not made up of atom, but
instead made up of the four elements: Earth, Fire, Water, and Wind. He believed
that all the materials on earth are made up of small amounts of each of these 4
elements. Even though Aristotle’s theory was incorrect, his idea was widely
more accepted than Democritus’s atomic theory. In the late 1800’s John Dalton
was an  English chemist, physicist, and meteorologist. He is best
known for proposing the modern atomic theory. Dalton’s modern atomic theory
states that all matter is made of atoms, All atoms of the same element are the
all very much identical, and that all atoms cannot be created or
destroyed. 

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In
the late 1800’s around the same time as when John Dalton was creating the
modern atomic theory, there was another English physicist and a Nobel Laureate
in Physics by the name of  Joseph John
Thomson or J. J. Thomson.  Thomson’s
discovery lead him to believe that the atom could be divided. He also found a
negatively charged part of the  atom
known as the electron. Thomson discovered the electron by experimenting with a
Crookes, or Cathode ray tube. A Cathode ray tube is a high-vacuum tube in which
cathode rays produce a luminous image on a fluorescent screen, used chiefly in
televisions and computer terminals. He called his theory The Plum Pudding
Model.

The
next discovery was actually from  a
Zealand-born British physicist who worked alongside J. J. Thomson. His name is
Ernest Rutherford and he became known as The Father of Nuclear Physics.
Rutherford is responsible for the discovery of the positively charged particles
known as protons. In order to find the discovery of protons, Ernest used an
experiment known as the Gold-Foil experiment. For Rutherford’s gold-foil
experiment, he used radioactivity to shoot alpha particles at the gold foil.
You’d expect all of them to pass through but 1 in 1000 of them bounce back or
deflect off the gold foil. He thought that in order for the alpha particles to
bounce back that it must of hit something so small and so dense. By 1932 him
and his colleague James Chadwick had found that the nucleus is made up of two
kinds of particles, positively charged protons and electrically neutral
neutrons.

James
Chadwick was an english physicist who in 1932 discovered neutrons followed up
by  the nucleus. Chadwick found out that
the nucleus does not have a positive charge nor a negative charge, but instead
contributes the atomic weight with the same effect as a proton. With this
discovery of the nucleus this had inspired the U.S. begin serious research on
atomic weaponry such as the atomic bomb. In WWII Chadwick was part of the
project “Tube Alloys” where he carried out his research and knowledge of the
nucleus to help the british government. The working conditions for Chadwick
were not easy in his laboratory in Liverpool because of  the German Air Force airships were frequently
bombing the neighborhood.