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D ALTON B IOGRAPHICAL
I NFORMATION
John Dalton was born on September 6, 1766 and died on July 27,1844. He
worked as a chemist, physicist, and meteorologist in England. He was the son
of a Quaker weaver just outside of Cumberland, England. He was appointed to
teacher of mathematics and natural philosophy at the New College in
Manchester in 1793. He retired from this position in 1800 due to the financial
constraints of the college and became a private tutor. Dalton had
deuteroanopia (or color blindness) so this was often a subject he studied.
Dalton also performed work on atomic theory, gas laws, and atomic weights.
Dalton suffered from a minor stroke in 1837 and 1838 leaving him with a
speech impediment. He was still able to perform his experiments but after
suffering from several more strokes he died in 1844.
D ALTON A TOMIC T HEORY

Elements are made of tiny particles called atoms.

All atoms of a given element are identical

The atoms of a given element are different from those
of any other element; atoms of different elements can
be distinguished from one another by their respective
relative weights.

Atoms of one element can combine with atoms of
other elements to form chemical compounds.

Atoms cannot be created, divided into smaller
particles, nor destroyed in the chemical process.
R UTHERFORD B IOGRAPHICAL
I NFORMATION
Rutherford was born in Brightwater, New Zealand on August
30, 1871. He died on October 19, 1937 in Cambridge,
England. He worked in the fields of chemistry and physics.
He is considered the father of nuclear physics. He was
awarded the Nobel Prize in Chemistry in 1908. Rutherford
received his bachelors and masters degrees from
Canterbury University and then continued his studies at
Cavendish Laboratory at the University of Cambridge. He
was knighted in 1914.
R UTHERFORD A TOMIC
T HEORY
Rutherford’s contributions to atomic theory include his gold foil
experiment. In this experiment he worked to prove the existence of
charges in each atom is different. In the gold foil experiment he set a
beam of alpha particles into a thin sheet of gold foil. Zinc sulfide
surrounded the gold foil (except where the beam came through). The
zinc sulfide lights up when it is struck by the beam (so he could tell were
the particles were hitting). The results of his experiment was that the
particles hit everywhere on the zinc sulfide. He proved that there was a
centralized charge (later called the nucleus). Although he could not
prove if the charge was positive or negative.
T HOMSON B IOGRAPHICAL
I NFORMATION
J.J. Thomson was born in 1856 in Cheetham Hill, Manchester in England.
His father died when he was only sixteen years old. He studied
engineering at the University of Manchester. He became a professor of
physics in 1884. He was awarded the Nobel Prize in Physics in 1906. He
is recognized for his work in discovering the electron, isotopes and mass
spectrometry. He is credited for discovering that Hydrogen only has one
electron and the natural radioactivity of Potassium. Rutherford was one
of his students at Cambridge. He died on August 30, 1940 in Cambridge.
T HOMSON A TOMIC
T HEORY
Thomson is credited for discovering the
electron in 1897. He was unsure about how it
fit into the atom though. So he developed
the plum-pudding model (shown to the left).
In this model he hypothesized that the
electrons were the negatively charged
“plums” in a sea of positively charged
“pudding”. He pictured that both positively
and negatively charged particles were
contained in the nucleus of the atom.
B OHR B IOGRAPHICAL
I NFORMATION
Niels Bohr was born on October 7, 1885 in Copenhagen, Denmark. He
worked extensively in the field of Physics. He received the Nobel Prize
in Physics in 1922. Bohr attended Copenhagen University in 1903 where
he studied philosophy and mathematics. After winning awards in
Physics he pursued his post-doctorate work under J.J. Thomson in
Cambridge. Then he studied under Rutherford. Bohr became a
professor at the University of Copenhagen. Bohr died on November 18,
1962 in Copenhagen.
B OHR A TOMIC T HEORY

First to introduce the theory that electrons travel
around orbits around the positively charged
nucleus (shown in the figure on the left).

Determined that the chemical properties of an
atom are determined by the outermost orbit.

He found that the rotation is comparable to the
earth’s rotation around the sun. Instead of
gravity, electrons are pulled in to the atom by the
electrostatic force.
Dalton
-Biographical Information
-Atomic Theory
Rutherford
-Biographical Information
-Atomic Theory
Bohr
-Biographical Information
-Atomic Theory
Thomson
-Biographical Information
-Atomic Theory
C ONCLUSION
Each scientist’s discoveries are interconnected. Many of them even studied under
each other. Dalton started it all out by helping us to understand that each atom is
different. He discovered that each atom had its own weight and properties, but he
could not explain why this was the case. J.J. Thomson picked up on Dalton’s
discoveries and added that each atom has electrons. He knew about this property,
but he described that it was just a random mixture of positively and negatively
charged particles. Rutherford picked up on Thomson’s experiments by doing his
gold-foil experiments, that proved that Thomson was right about each atom
having electrons. Rutherford further went to prove that instead of a random
mixture it was ordered (the negatively and positively charged particles were not
located in the same place). Rutherford had a hard time explaining exactly what
the atom looked like, until Bohr came around (who also studied under Thomson).
Bohr was able to put it all together. He took what was understood from Dalton,
Thomson, and Rutherford, and developed his model, which we still use today! See
this elaborate web of work in the flowchart link below.
Click here to find
more information
N EAT WEBSITE
For a big picture look at atomic theory (from 460 BC
to present) visit this website:
http://www.google.com/#q=atomic+theory+history&hl=en&tbs=tl:1&tbo=u&e
i=48muSsu6IIjosQP1wMHLCw&sa=X&oi=timeline_result&ct=title&resnum=11
&fp=b7f806229eacb72c
I
LEARNED :

I learned how to create and use a word web.

I learned how to effectively use the hyperlink function.

I learned how this could be a good alternatively to paper
writing in class (or a good lead into paper writing). It
helps students organize research.

I learned how to transfer “video”-pictures from the
internet

I learned to use the Microsoft website to download cool
backgrounds and sounds.

The value of sharing (how this can be implemented in
the classroom).