Transcript Amadeo Avogadro - Chemistry Outreach 2000

Born June 9, 1776
Died July 9, 1856
The ideas of Cannizarro and Loschmidt
combined the atomic weight of an atom with
the rough size of the molecules. Therefore,
with these two pieces of information, it was
then possible to find Avogadro’s number. The
1st reasonable estimates of the number
occurred in the late 1800’s.
BIOGRAPHY
He was born, raised and died in Turin,
Italy.
He was schooled in law at home.
He became a lawyer at the age of 20 and
practiced law for 3 years.
To this day, the modern method of
calculating Avogadro’s number is to use the
density of a crystal, the relative atomic mass
and the unit cell length.
He was very successful as a lawyer, but his
interests lied in Natural Philosophy, which
we now know as Science.
He attended college for Mathematics and
physics at the college of Vercelli.
He married Felicita Mazze and together,
they had 6 children.
He work was based on the journals of
Joseph Gay-Lussac in 1809. Gay-Lussac
studied the chemistry of gasses reacting and
their volume ratios. But, his work was not
complete and this is where Avogadro stepped
in.
CONTRIBUTIONS TO CHEMISTRY
Avogadro believed in the idea of both
atoms and molecules. At this point in time
(1811), Dalton had confused the idea
separating the molecule and the atom.
Avogadro believed that equal volumes of all
gasses under standard conditions contain the
same number of molecules. This theory is
known as Avogadro’s Principle.
Additionally, his principle was nearly
forgotten until Stanislao Cannizarro
pressingly presented it to the Karlsnine
Conference in 1860, almost 50 years after
Avogadro had come up with it. He had
passed away four years earlier.
When Avogadro lived, there was no known
idea of a mole. But, Avogadro believed that
since there were atoms and molecules, that
there existed an equal number of molecules
for equal volumes of gasses under standard
conditions. Today that equal number of
molecules is known as Avogadro’s Number.
Moreover, Avogadro did not determine the
actual value of the number which bears his
name.
DETERMINATION OF THE
NUMBER
Overall, Avogadro was the catalyst in being
able to generalize what number of molecules
are present in any given chemical reaction.
6.0221367 x 1023
Sources:
http://www.woodrow.org/teachers/chemistry/institutes
/1992/Avogadro.html
http://avogadro.che.hw.ac.uk/avoga.html
http://moleday.org/avogadro.html
Around 1860, Cannizarro used Avogadro’s
Drs. Boyles and McDowell
ideas to work further upon this idea of an
“equal number of molecules.” Cannizarro
found a way to obtain a set of atomic
Chemistry Outreach Spring 2001
weights, based upon oxygen, which has an
South Dakota School of Mines and Technology
atomic weight of 16.
Rapid City, SD 57701
Additionally in 1865, Loschmidt used a
mix of liquid density, gaseous viscosity and
the kinetic theory of gasses to establish the
rough size of molecules.
Heidi Peterson