Atomic timeline

The Atom A history and
discovery
of the atom

By: Ryan Hong

General Information of the Atom

Atom: The smallest and most basic form of matter
An Idea: The first ever recorded idea of an atom is by Democritus in
440 B.C.E. Democritus thought that everything is made of these small
particles called atoms. They could not be created nor destroyed.
General Information:
Every element of the periodic table has it's own type of atom. Atoms
consist of three subatomic particles, electrons, protons, and neutrons,
they also vary by the number of neutrons, electrons, and protons they
contain.

Democritus (460-370 BC)

Atomic Theory (440 B.C.E):
Democritus is responsible for creating the
early idea of the atom. Democritus wondered
if mater could be divided into smaller pieces.
His theory goes as follows, everything is
make of atoms, inside of atoms is empty
space, they vary in different shapes and
sizes, and atoms are indestructible. This
theory paved the way for future scientists to
experiment and unravel the misteries the
atom.

Democritus's Atomic Model Real world analogy: Books

Aristotle (384-322 B.C.E)

(450 B.C.E) Aristotle did not agree with the
theory proposed by Democritus. Aristotle
thought that objects were not made by atoms,
but rather the five elements, Air, earth, water,
fire, and Aether. Aether is what Aristotle
believed that stars were composed of. He
thought that everything was made of either one
element, or a mixture of multiple. Aristotle is
responsible for disproving the atomic theory,
making people ignore the theory for thousands
of years.

Real world
analogy:

Aristotle's Atomic Elements of
model: the world

John Dalton (1766-1844)

Dalton's Atomic theory (1803):
John Dalton is responsible for greatly
improving Democritus's theory on the atom.
Everything is made of small particulates called
atoms. Atoms can neither be created or
destroyed, but re purposed. Each element has
their own unique atom. Atoms from different
elements have different mass and chemical
properties.

Dalton's atomic Real world analogy: Legos
model:

JJ Thompson (1856-1940)

Cathode ray Tubes experiment (1897):
JJ Thompson is responsible for the discovery of the electron.
He discovered the electron while preforming a Cathode ray
tube experiment. Gas enters a field with two ionized plates on
the side. The plates are charged a heated cathode, thus
creating a cathode ray. Thompson went out to prove that the
ray consists of small negativity charged particles called
electrons. To prove this, Thompson put two oppositely charged
magnets around the ray. The ray was deflected away from the
negatively charged magnet and toward the positive one. This
showed that the ray consisted of negatively charged electrons.

JJ Thompson atomic Real World analogy: Plum pudding model
model:

Ernest Rutherford (1871-1937)

Gold Foil experiment (1910):
Ernest Rutherford is responsible for the
discovery of the nucleus in the atom. Rutherford
discovered it while preforming a gold foil
experiment. The experiment consisted of shooting
radioactive alpha particles at a sheet of gold only
one thousand atoms thick. He expected the
particles to go through the gold, but every once in a
while a particle would bounce back from the sheet.
This meant that there was something bigger than
the alpha particle in the gold sheet. This he
concluded to be the nucleus of the atom.

Rutherford's atomic Real world
model: analogy:

Avocado
(atom) with pit

(nucleus)

Niels Bohr (1885-1962)

Bohr Atomic Model (1913)

Niels Bohr's biggest contribution to physics is the
Bohr atomic model. This model refines previous
models as well as fixing holes in previous theories.
Rutherford's model had a fatal flaw that had to do
with electrons. In Rutherford's model a charged
particle moving on a curved path releases
radiation, the electrons would lose energy and
crahs into the nucleus. Bohr fixed this problem by
refining the atomic model. Bohr made it so that the
larger electrons had a larger orbit around the
nucleus and a small orbit for the smaller electrons.

Bohr's atomic Real world
model: analogy:

Planets
orbiting the

sun

Erwin Schrodinger (1887-1961)

Quantum Mechanical model of the atom (1926):

Erwin Schrodinger took the previous atomic models and
thought about the electrons in those models. Instead of
picturing the electrons orbiting individually around the
nucleus. He proposed and idea that the electrons orbit
in a cloud rather than individually. His ideas paved the
way for future scientist to discover more about the atom.

Schrodinger's atomic Real world analogy: Cotten Ball
model

Albert Einstein (1879-1955)

Existance of the atom (1905):
Albert Einstein mathematically proved that atom exist.
Einstein did this by observing tiny particles suspended in
liquids. He observed that the particles moved around in a
very spratic and random way, moving many directions. But
the larger particles are not just moving randomly, they are
bouncing off of smaller particles known as atoms. Einstein
used a consept known as Brownian Motion. Brownian
Motion describes the motion of particles suspended in a
liquid. einstein calculated how large an atom is, by looking
at how much the suspended particles move.

Einsteins atomic Real world analogy: penguins
model: in relation to icebergs

Werner Heisenberg (1907-1976)

Uncertainty Principle (1927):

The uncertainty principle is a principle that shows
that you can never know the exact position and
exact speed of an object. Heisenberg's principle
shows people that it is impossible to find an exact
location of an electron in an atom.

Real world analogy: fining your car on
the moon (the car is to small to be found
in comparison to the moon

Heisenberg atomic model:

Bibleography

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