Disclaimer: The article below is derived from an article of another author (reference provided).
From Alchemy to Chemistry to Artificial
Transmutation of Elements
(derived from
“From Alchemy to Chemistry” by Michelle Feder, pp.3-11)
Understanding
Alchemy
Many of the earliest chemists,
physicians, and philosophers were also alchemists. Alchemy was an early
philosophical and spiritual field of study that combined chemistry with
metalwork. But it was also an investigation of nature. The goals of Alchemy were:
a. To find the “elixir of life”. It was thought that this
magical elixir would bring wealth, health and eternal life.
b. To find or make a substance called the “Philosopher’s
stone.” When heated and combined with Cu or Fe, it would turn into Au, which
was once thought to be the highest and purest form of matter.
c. To discover the relationship of humans to the cosmos
and use that understanding to improve the human spirit.
The roots of Alchemy are
difficult to track down. In the East, in India and China, alchemy started
sometime before the Common Era (B.C.E). They began with meditation and medicine
designed to purify the spirit and body to thereby achieve immortality. In the
West, alchemy probably evolved from Egyptian metallurgy as far back as the
fourth millennium B.C.E.
Let’s start at a time and with a
person we are most familiar with and that is Aristotle in the early 300 B.C.E.
Recall that in the previous lesson, it was discussed that Aristotle believed
that all matter was made of the four elements Earth, Water, Air and Fire. He
was prominent and what he declares matters.
Robert Boyle
Roughly 2,000 years later, in
the golden age, a natural philosopher by the name of Robert Boyle (1627–1691)
came up with what we call today as the “Boyle’s Law”. It states that the volume
of a gas decreases as the pressure on it increases.
The focus of Boyle’s study was
the Transmutation of elements. He claimed to have changed Au into Hg by means
of “quicksilver”, the ingredients of which he did not reveal. Central to Boyle’s
efforts was his “corpuscular hypothesis”. He believed that all matter consisted
of arrangements of tiny identical particles called corpuscles. Transforming Cu
to Au seemed to be just a matter of rearranging the pattern of its corpuscles
into that of gold.
Aristotle’s Four-Element theory
was still around and Boyle sought to overthrow it. He recognized that certain
substances decompose into other substances. At some point though, there are
substances that cannot be broken down any further. For instance, water
decomposes into H and O when it is shot through with electricity. But H and O
cannot be broken down into anything smaller. These fundamental substances that
couldn’t be broken down further, he called Elements. His claims were backed by
experimentations and a more scientific Chemistry branched out from the more
spiritual Alchemy.
Antoine-Laurent
Laviosier and Dmitri Mendeleev
Among the most significant of
the post-alchemical chemists were Frenchman Antoine-Laurent Laviosier
(1743-1794) and Russian Dmitri Mendeleev (1843-1907).
In 1789, Laviosier wrote the first true chemistry
textbook. Here, he made a list of metallic and non-metallic elements. For this,
among many more contributions in the field of chemistry, he earned the nickname
“Father of Modern Chemistry”.
By the late eighteenth century,
the field of chemistry had fully separated from traditional alchemy- with the
help of Dalton’s Atomic Theory of course- and more elements were discovered and
studied.
In 1869, with 63 known elements, Mendeleev
showed that these elements could be arranged in a periodic relationship
(regular and recurring) to each other.
This became the first Periodic Table of Elements. It was compiled on the
basis of arranging the elements in ascending order of atomic weight and
grouping them by similarity of properties. He left space for new elements yet
to be discovered.
With the empty spaces in Mendeleev’s periodic table, the
discovery of more elements became much easier and more targeted. However, a
dilemma later arises: “Several elements appear to be misplaced. Their
properties are not aligned as predicted.” When Mendeleev died, chemists were
sure that, contrary to Mendeleev’s arrangement, Iodine followed Tellurium in
the Periodic Table. There was something odd about their relative atomic masses.
Henry Moseley
Henry Moseley (1887-1915), a
British chemist, studied under Rutherford and brilliantly developed the
application of X-ray spectra to understand atomic structure. Recall that
Rutherford was known to have discovered the nucleus of an atom, as well as the
protons in it. He was in collaboration with other scientists and one of those
was Henry Moseley.
What exactly did Moseley do? He
measured the frequency of the X-rays given off by different elements. Each
element gave a different frequency and he found that this frequency was
mathematically related to the position of the element in the Periodic Table –
he could actually measure atomic number. And atomic number was actually the
number of protons! In 1913, he published the results of his study. This
resulted in a revised, more accurate positioning of elements in the Periodic
Table, which is arranging it by increasing atomic number.
TRANSMUTATION
So now that we have established
the facts about atomic number and the role it plays in an element’s identity,
we can talk about transmutation. Artificial Transmutation, to be exact.
Transmutation is the act of changing a substance,
tangible or intangible, from one form or state into another. To the alchemists
of old, this meant the conversion of one physical substance into another,
particularly base metals such as lead into valuable silver and gold. To the
modern scientists, this means the transformation of one element into another by
one or a series of nuclear decays or reactions. Is this possible? We now know
that it is.
Because each element has a
different but fixed number of protons in the nucleus of the atom, which is the
atomic number, the transmutation of one chemical element into another involves
changing that number. Such a nuclear reaction requires millions of times more
energy than was available through chemical reactions. This massive amount of
energy required to alter an atomic nucleus came in the form of Particle
Accelerators (more commonly referred to as Atom Smashers).
Artificial Transmutation of
elements involves either of the two nuclear process namely: Nuclear Fusion (a
heavier atomic nucleus is made from two smaller atomic nuclei) and Nuclear
Fission (an atomic nucleus splits into two smaller nuclei of roughly equal
mass). A Nuclear Chain Reaction could involve both.
Over the second half of the
twentieth century, the artificial transmutation of one element into another has
become commonplace. In fact some two dozen synthetic elements have been
produced so far by nuclear transmutation reactions. The artificial elements
include the elements technetium (atomic number Z = 43), promethium (Z = 61) and
the transuraniums (Z > 92).
In chemistry, transuranium
elements, also known as transuranic elements, are the chemical elements with
atomic numbers greater than 92, which is the atomic number of uranium. These
elements were produced by bombarding a heavy atomic nucleus with a smaller
ionized particle via particle accelerator.
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