By: Ashley Morgan
Periods: 3rd & 4th
Atomic Theory Timeline
Atoms are the fundamental building blocks of matter.
The Atomic Theory
442 B.C. DemocritusDemocritus stated
that all matter is made up of
atoms. He also stated that they are so small that they can’t be divided,
and they entirely fill up the space they’re
in.
384-322 B.C. Aristotle
Aristotle provided the method of
gathering scientific facts, which proved as the basis for all
scientific work.
1777 Antoine LavoisierLavoisier is the founder of modern
chemistry. He showed that chemical
elements were neither created nor destroyed,
just combined into different compounds in chemical reactions. In
other words, he distinguished between
an element and a compound.
1799 Joseph Louis Proust
Proust is known for the Law of Definite proportions. This
states that a chemical compound
always contains exactly the same
proportion of elements by mass.
1803 John Dalton
John Dalton formed the atomic
theory, which states that all
matter is composed of tiny,
indestructible particles called
atoms. They are all alike and have the
same atomic weight.
1832 Michael Faraday
Faraday developed the
Laws of Electrolysis. This is the splitting of
molecules with electricity.
1896 Henri Becquerel
Becquerel is noted for the discovery of
Radioactivity.
1898 Marie & Pierre CurieThe Curies stated
that radioactive materials cause atoms to break
down spontaneously,
releasing radiation in the form of energy and
subatomic particles.
1898 J.J ThomsonThomson discovered the electron
and developed the plum-pudding model of the atom.
1900 Max Planck
Planck stated that energy is radiated
in small units, which he called quanta.
1905 Albert Einstein
Einstein stated light was made up of
different particles, that, in addition to wavelike behavior,
demonstrate certain properties unique to
particles.
1908 Robert Milikan
Millikan was able to find out the
electric charge of the electron.
1909 Ernest RutherfordRutherford used the
results of his gold-foil experiment to state that all the mass of an atom were in a small
positively-charged ball at the center of
the atom.
1913 Neils Bohr
Bohr stated that the electrons moved
around the nucleus in successively
large orbits.
1931 James ChadwickChadwick is noted for the discovery of the neutrally-
charged neutron.