Posted
on January 3, 2015
 |
This sculpture of Rutherford "splitting the
atom" and discovering the nucleus (although
in reality, he wore clothes as he did his
famous experiments) is found in Eastern
China, in the Qingpu Oriental Land Garden. |
For
centuries people had tried to create gold—precious, beautiful,
heavy, shiny gold—out of “base metals.” All the greedy
tinkering with materials in this attempt—experimental
messing-around that went by the name alchemy—actual
grew into the experimental methods of an actual science, chemistry.
(Do you see the relation of the words alchemy
and chemistry?)
But,
it turns out, no amount of chemical tinkering can turn one element,
such as lead, into another. No gold for the alchemists, no matter how
hard they tried!
On
this date in 1919, Ernest Rutherford did not create gold out of
another element, but he did use gold foil in his experiment, and he
did succeed in—for the first time ever—using science to change
one element into another:
He sent alpha particles through thin gold foil and into pure nitrogen.
And he created oxygen.
(Alpha
particles are helium nuclei: two protons and two neutrons. Actually,
when Rutherford sent the helium nuclei into pure nitrogen, he not
only created oxygen but also leftover protons.)
This
was an incredible step forward for physics, but in a way it is all of
a piece with Rutherford's other accomplishments. Because of
Rutherford's experiments with radioactive materials, the gold foil
experiment, and later a fully controlled splitting of a nucleus,
Rutherford was able to develop a model for atoms that was much more
accurate than earlier models.
Um...what
exactly are atoms?
Matter
is largely made up of atoms. In the way olden days, people used atom
to mean the smallest possible quantity of matter, which could not be
further divided.
Indivisible?
Then...why do we need a model? If it's indivisible, how could there
be structure?
Of
course, the important words in the last sentence are “in the way
olden days.” Modern scientists of the early 1900s knew that there
must be structure in atoms, and although they could not be divided by
chemical means, Rutherford showed that natural radioactivity was in
fact atoms disintegrating into smaller parts. Theoretically, humans
could deliberately “split atoms.”
So
what model of atomic structure did scientists come up with?
In
1904 J. J. Thomson suggested the plum pudding model of an atom.
Electrons
had been discovered in 1894, and Thomson suggested that the
negatively-charged electrons were scattered about in a sort of
positively-charged “soup” or pudding, like raisins in plum
pudding or blueberries in muffin batter.
And
Rutherford disproved this model?
When
Rutherford ran his gold foil experiment, he hypothesized that the
alpha particles would continue through plum-pudding atoms
uninfluenced by their consistent “mixture” type of structure.
However, he discovered that a small portion of alpha particles were
deflected, which would only make sense if the positive charge in an
atom was found only in a small central area rather than throughout
the entire atom.
Do
we still use Rutherford's model?
Yes
and no. Thanks to Rutherford and Niels Bohr, we know that protons (+
charge) and neutrons (no charge) are in a central nucleus, but our
quantum physics insists that this familiar looking atomic model,
which has electrons orbiting the nucleus rather like planets orbit
the sun...
...is
too simplistic. Instead, electrons form a “probabilistic” cloud
around the dense nucleus.
Also
on this date:
Fruitcake Toss Day
Plan
ahead:
Check
out my Pinterest pages on:
And
here are my Pinterest boards for:
Actually,
gumdrops are more than just candy – they are a great building
material!
Gumdrops
are made of gelatin, coloring and flavoring, and of course lots of
sugar. They are available in fruit or spice flavors.
The
Apollo 9 Command module was nicknamed “Gumdrop” because of its
shape. Also, the fact that it arrived at Cape Kennedy in a blue
cellophane wrapper didn't hurt!
