Download History of the Atom

History of the Atom
Scientists and Their Contribution to
the Model of an Atom
History of the Atom - Timeline
Antoine Lavoisier
makes a substantial
J.J. Thomson
number of contributions
discovers the
to the field of electron and
Chemistry proposes the
Plum Pudding
1766 – 1844
Model 1871
in 1897
– 1937
Niels Bohr
proposes
the Bohr
Model in
1913
1887 – 1961
James
Chadwick
discovered
the neutron
in in 1932
1700s
1800s
1900s
460 – 370 BC
0
Democritus
proposes
the 1st atomic
theory
1743 – 1794
Erwin
John Dalton
Ernest Rutherford
Schrodinger
proposes performs
his
the Gold Foil
describes
1891 – 1974
atomic theory
Experiment
in
in 1909
the electron
1803
cloud in 1926
1885 – 1962
Click on picture for more information
1856 – 1940
Democritus
(460 BC – 370 BC)
• Proposed an Atomic Theory
(along with his mentor
Leucippus) which states that
all atoms are small, hard,
indivisible and indestructible
particles made of a single
material formed into
different shapes and sizes.
• Aristotle did not support his
atomic theory
Image taken from: https://reichchemistry.wikispaces.com/T.+Glenn+
Time+Line+Project
Antoine Lavoisier
(1743 – 1794)
Image taken from:
www.ldeo.columbia.edu/.../v1001/geo
time2.html
 Known as the “Father of Modern
Chemistry”
 Was the first person to generate a list of
thirty-three elements in his textbook
 Devised the metric system
 Was married to a 13-year old Marie-Anne
Pierette Paulze; she assisted him with
much of his work
 Was a tax-collector that was
consequently guillotined during the
French Revolution
 Discovered/proposed that combustion
occurs when oxygen combines with other
elements
 Discovered/proposed the Law of
Conservation of Mass (or Matter) which
states, in a chemical reaction, matter is
neither created nor destroyed
John Dalton
(1766 – 1844)
 In 1803, proposed an Atomic Theory
which states:
o All substances are made of atoms;
atoms are small particles that
cannot be created, divided, or
destroyed.
o Atoms of the same element are
exactly alike, and atoms of
different elements are different
o Atoms join with other atoms in
whole number ratios to make new
substances
 Calculated the atomic weights of many
various elements
 Was a teacher at a very young age
 Was color blind
Image taken from:
chemistry.about.com/.../JohnDalton.htm
J.J. Thomson
(1856 – 1940)
Image taken from:
www.wired.com/.../news/2008/04/d
ayintech_0430
 Proved that an atom can be divided
into smaller parts
 While experimenting with cathoderay tubes, discovered corpuscles,
which were later called electrons
 Stated that the atom is neutral
 In 1897, proposed the Plum Pudding
Model which states that atoms
mostly consist of positively charged
material with negatively charged
particles (electrons) located
throughout the positive material
 Won a Nobel Prize
 cathode ray tube
Thomson’s Plum Pudding Model
•Thomson’s Plum Pudding model is a +
charge sphere that has (- )charged
electrons scattered inside, like “raisins” in
“plum pudding”.
•Overall, the atom is neutral atom
because the atom had the same number
of positive and negative charges.
•From Thomson’s experiments, scientists concluded that
atoms were not just neutral spheres, but somehow were
composed of electrically charged particles.
•The balance of positive and negative charge supports the
neutral atom.
Ernest Rutherford
(1871 – 1937)





In 1909, performed the Gold Foil
Experiment and suggested the following
characteristics of the atom:
o It consists of a small core, or nucleus,
that contains most of the mass of the
atom
o This nucleus is made up of particles
called protons, which have a positive
charge
o The protons are surrounded by
negatively charged electrons, but most
of the atom is actually empty space
Did extensive work on radioactivity (alpha
& beta particles, gamma rays/waves) and
was referred to as the “Father of Nuclear
Physics”
Won a Nobel Prize
Was a student of J.J. Thomson
Was on the New Zealand $100 bill
Image taken from:
http://www.scientificweb.com/en/Physics/Biographies/Er
nestRutherford.html
Gold Foil Experiment
• Rutherford directed a narrow
beam of alpha particles (+
charges) at a thin piece of
gold foil.
• Based on observations from
other experiments involving
alpha particles, he predicted
that the (+) charges would
go through the foil
Results from Gold Foil Experiment
•Rutherford found that every
once and a while, a + particle
was deflected bounced back.
(about 1% of the time)
•Why?
•Because the + charge hit a
central mass of positive charge
and was repelled.
The Gold Foil Experiment
Rutherford’s Planetary Model
• To explain his
observations,
Rutherford developed a
new model
•The electrons orbit
the nucleus like the
planets revolve around
the sun.
Niels Bohr
(1885 – 1962)
Image taken from:
commons.wikimedia.org/wiki/File:Ni
els_Bohr.jpg
 In 1913, proposed the Bohr
Model, which suggests that
electrons travel around the
nucleus of an atom in orbits or
definite paths. Additionally, the
electrons can jump from a path
in one level to a path in another
level (depending on their energy)
 Won a Nobel Prize
 Worked with Ernest Rutherford
Erwin Schrodinger
(1887-1961)
• In 1926, he further explained
the nature of electrons in an
atom by stating that the exact
location of an electron cannot be
stated; therefore, it is more
accurate to view the electrons in
regions called electron clouds;
electron clouds are places where
the electrons are likely to be
found
• Did extensive work on the Wave
formula  Schrodinger equation
• Won a Nobel Prize
Image taken from:
nobelprize.org/.../1933/schrodinger
-bio.html
James Chadwick
(1891 – 1974)
 Realized that the atomic mass of
most elements was double the
number of protons  discovery
of the neutron in 1932
 Worked on the Manhattan
Project
 Worked with Ernest Rutherford
 Won a Nobel Prize
Image taken from:
www.wired.com/.../news/2009/02/d
ayintech_0227
Progression of the Atomic Model
-
-
-
- --+-
-
+
- -
The structure of an atom, according to:
Electron Cloud
Democritus
James
Ernest
Erwin
Neils
Schrodinger
Chadwick
Rutherford
Bohr&
J.J.
Thomson
John Dalton
Review
Overall Reviewhttps://www.youtube.com/watch?v=thnDxFdkzZs
JJ Thompson- discovery of electron
https://www.youtube.com/watch?v=Rb6MguN0Uj4
Gold foil Experiment –discovery of nucleus
https://www.youtube.com/watch?v=dNp-vP17asI
Review
Who is the father of atomic theory?
Dalton
What was the first model of the atom?
Dalton’s Tiny Ball Model
What are Dalton’s 3 Laws?
Law of Conservation of Mass, Law of
Constant Composition, Law of Multiple
Porportion
Review
How were Thomson’s and Dalton’s model
different?
Dalton’s model was 1 sphere that cannot be
divided, Thomson had the plum pudding
where electrons are randomly spread
throughout a positively charged sphere.
What did Thomson find out?
Atoms have electrons, they have a - charge
Review
What were Rutherford’s conclusions from the
Gold Foil Experiment?
• Atom has a positively charged nucleus
• electrons are outside,
• atoms are mostly empty
• Nucleus contains most of the mass.