Today, we wonder how to draw an atom. The
University of Houston's College of Engineering
presents this series about the machines that make
our civilization run, and the people whose
ingenuity created them.
It was gentle John Dalton who
finally sorted out the rumblings of late
18th-century chemists and gave us a proper atomic
theory. Dalton lived a quiet life of modest means.
He was a bachelor and a devout Quaker who showed
little passion of any kind. One subject did elicit
a flare of anger, though. That was the debate over
how to represent chemical combinations. And therein
hangs our tale.
Dalton spent his life licking the wounds of an
early failed love. For the rest, he tutored
students, he had his one nightly pint of ale, and
he studied. His only pastime was lawn bowling, and
that becomes part of our story. His friends
described him as awkward, strident, without social
grace, and admirably independent.
In 1802, when he was 36, he began forming and
setting forth his atomic theory of matter. He
showed how matter is made of elemental atoms, and
that atoms of each material have a distinct weight.
He didn't have the weights quite right. (Today we
know that oxygen weighs 16 times as much as
hydrogen, carbon 12 times as much, and so forth.)
But Dalton clearly saw that when elements combine,
they have to do so in fixed proportions.
Next he needed a scheme of notation for chemical
reactions. When you and I took chemistry, we wrote
formulas like
2H2 + O2 yields
2H2O
But that's what displaced Dalton's original
notation. When he wrote that formula, he used round
circles to identify the atoms. His phosphorus
looked like a Mercedes hood ornament. Oxygen was an
empty circle, and hydrogen had a dot in the middle.
For water, H2O, he used
three circles, two with dots in the middle and one
open.
Dalton argued strenuously against our modern
notation. And it really was no minor matter. You
see, a debate had been raging among scientists. Do
we make grand generalizations about nature, or do
we just report the facts, carefully and accurately?
Atoms were an ancient theoretical idea from before
Aristotle. But the prevailing mood in 1802 was to
take Dalton's theoretical atoms as only a metaphor
for rules of chemical combination. They weren't
real.
But Dalton loved lawn bowling, and his atoms were
as real and corporeal as those wooden bowling
balls. Some scientists want notation to be
abstract. Others want their symbols to
representational. That was a major issue in the
famous Newton/Leibnitz battle over calculus
notation, and it was certainly at issue here.
Yet more than notation was at stake here.
Scientists who accepted Dalton's theory
backed away from his pictorial notation
because that suggested that they were accepting the
atoms themselves. Dalton knew perfectly well that
chemistry couldn't move forward without such
an acceptance. So his legacy reached beyond his
theory. It took another 75 years, but we finally
granted reality to his invisible bowling
balls. We finally created atomic physics.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
Greenway, G., John Dalton and the Atom.
Ithaca: Cornell University Press, 1966.
John Dalton & the Progress of Science.
(D.S.L. Cardwell, ed.). New York: Manchester
University Press, Barnes and Noble Inc., 1968.
von Baeyer, H. C., Nota Bene. The Sciences,
January/February 1999, pp. 12-15.
See also the article on John Dalton in the
Dictionary of National Biography.
John Dalton from an engraving by Worthington
Some of Dalton's symbols for the elements
with his estimates of molecular weight
The Engines of Our Ingenuity is
Copyright © 1988-1999 by John H.
Lienhard.
