Atomic Model Timeline
Category: Outro
Atualizado: 26 out 2018
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Created byJason Powell
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JOHN DALTON (1766-1844 CE)
date of discovery (1803 CE)
All matter is made up tiny indivisible
particles called atoms (solid, hard,
impenetrable, movable particles) where
different atoms of elements are spheres
of different sizes and colors.
His atomic model provides much of the
framework that is used in modern
chemistry efforts.DMITRI MENDELEEV (1834-1907 CE)
date of discovery (1869 CE)
Created the first periodic table that
arranged the known elements according
to their of atomic mass and organized
them into groups possessing similar
properties.
His periodic table predicted the existence
of three new elements (gallium, scandium,
and germanium) and when these elements
were discovered, they fit correctly into the
three missing elements in his table.HENRY MOSELEY (1887-1915 CE)
date of discovery (1913 CE)
His work was used to reorganize
the periodic table based upon
atomic number instead of atomic
mass. He used x-ray tubes to
determine the charges on the
nuclei of most atoms.
Created the world’s first atomic
battery (beta cell) and he discovered
that an element’s atomic number is
identical to how many protons it has.J.J. THOMSON (1856-1940 CE)
date of discovery (1897 CE)
Discovered negatively charged
particles (electrons) using cathode
ray tubes and proposed the "plum
pudding" model of the atom which
consisted of a uniform sphere of
positive charge with negative electrons
embedded in the sphere.
Even though Thomson’s atomic model
was inaccurate and had a few drawbacks,
Thomson's model is important because it
introduced the notion that an atom
consisted of charged particles and it
provided the base for sevMARIE CURIE (1867-1934 CE)
date of discovery (1898 CE)
Atom is composed of particles
and the nuclei of heavy, unstable
elements lose mass (decay) and
give off energy (radioactivity).
Discovered unknown elements
polonium and radium and deduced
that radioactivity does not depend
on how atoms are arranged into
molecules, but rather that it originates
within the atoms themselves.ERNEST RUTHERFORD (1871-1937 CE)
date of discovery (1907 CE)
Fired alpha particles at gold foil and
deduced that the atom is composed
mostly of empty space with electrons
orbiting in a set, predictable paths
around fixed, positively charged nucleus.
Although his model was partially
inaccurate, it helped form the basis
of the quantum mechanics and helped
the future development of quantum
mechanics.HANTARO NAGAOKA (1865-1950 CE)
date of discovery (1904 CE)
Atom is a large, massive, positively
charged sphere, encircled by many
light-weight, negatively charged
electrons bound by electrostatic
forces analogous to Saturn's rings
(Saturn model).
His model predicted a massive
atomic center (nucleus) with
electrons revolving around the
nucleus and bound by electrostatic
forces. Both predictions were
successfully confirmed by Ernest
Rutherford in 1911.NIELS BOHR (1885-1962 CE)
date of discovery (1913 CE)
Atom is composed of negatively
charged electrons traveling in
separate orbits around a positively
charged nucleus. Atoms absorb or
emit radiation when electrons on
subatomic level jump between the
allowed and stationary states.
Discovered that the number of
electrons in the outer orbit
determines the properties of an
element.
Bohr’s work contributed significantly
to scientists' understanding of nuclear
fission.JAMES CHADWICK (1892-1974 CE)
date of discovery (1932 CE)
Atom is composed of a nucleus
containing neutrons (no electric
charge) and protons (positively
charged) with electrons (negatively
charged) orbiting the nucleus at
separate levels.
Discovered the existence of the
neutron by bombarding beryllium
with alpha particles.
His findings were pivotal to the
discovery of nuclear fission and
ultimately the development of
the atomic bomb.ERWIN SCHRODINGER (1887-1961 CE)
date of discovery (1924 CE)
Atom is composed of a nucleus
containing protons and neutrons
with electrons moving in a set of
waves around the nucleus (electron
cloud of probability).
Established the wave mechanics
formulation of quantum mechanics,
which portrayed electrons as waves,
spread out rather than in any given
location.LOUIS DE BROGLIE (1892-1987 CE)
date of discovery (1924 CE)
Atom is portrayed as a nucleus
surrounded by an electron cloud.
This model introduced the concept
of sub-energy levels.
Discovered the wave nature of
electrons and suggested that all
matter have wave properties
Inspired the birth of wave mechanics.Períodos
DEMOCRITUS (460-370 BCE)
Everything is composed of “atoms”,
which are physically indivisible.
Between atoms, there lies empty space.
The solidity of a material
corresponded to the shape of the
atoms involved.
Influenced others like the Roman
philosopher Lucretius in the 1st
century CE and other scientists
during the Scientific Revolution.ARISTOTLE (384-322 BCE)
Atoms do not exist and everything
is made up of 4 elements: earth (cool),
air (light), fire (hot), water (wet).
All matter is made up of varying levels
of all four elements to take on their
unique composition.
His refusal to accept atoms as a scientific
reality may have set the model of the
atom back for centuries.
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