What is an element and what does this have to do with water? (Part 1)
Even though for at least a couple of thousand years, if not more, people had been
wondering about the nature of matter, the stuff that surrounds us on a daily basis, and of
which we too are made, and even though a number of thinkers had put forward the idea
that matter must be composed of a limited number of fundamental constituent (dare I say
elemental) things, we really had no empirical evidence, and hence no reality-based proof
that this was so until not really all that long ago.
Source: http://archaeology.about.com/od/metallurgy/tp/Metal-History.htm
An example of what copper ore can look like. You can see how it would be relatively easy to hammer
this into basic metal tools.
This however is not to say that people thousands of years ago had not made the
technological discovery that some substances seemed to be somehow fundamental, or at
least irreducible: copper was the 1st metal to be discovered, mined and worked by our
species, perhaps as early as 10-odd thousand years ago in Anatolia. Since copper is often
found in its elemental state (or with just a light coating of its oxide), this ought not to be
too surprising. Gold, and then lead, silver, iron, carbon, tin, sulphur, mercury, zinc, arsenic
and antimony too were all discovered between about 7,000 and 3,000 years ago, some
because they are often found naturally in their pure state ((e.g. gold, silver & carbon),
others because there were relatively simple and straightforward means of purifying them
available (e.g. tin, iron & mercury).
Source: http://www.ras-international.org/eng/news/2010_11_copper-age-settlement-found-inserbia.html
Some 7,500 year-old copper tools found in what is now Serbia. These are amongst the oldest such
tools found, but presumably, the technology to produce them dates from a slightly earlier period, as
these tools seem to be fairly well developed. The difference between these tools and those found in
Anatolia somewhat earlier is that these seem to have been smelted from the ore, rather than beaten
from the raw metal.
Having this technology however is a far cry indeed from having a concept of the
elements in the sense in which we understand the concept today. The process which led to
our modern understanding of the elements began perhaps in the 1600s, with the work of
the alchemists who noted that some of the substances they worked with were irreducible,
and seemed to be fundamental in some way: elemental if you like.
Source: http://upload.wikimedia.org/wikipedia/commons/9/9f/Hennig_Brand_%28Joseph_Wrigh
t%29.jpeg
The alchemist in search of the philosopher's stone by Joseph Wright of Derby (The painting
illustrates the discovery of phosphorus by Hennig Brand in 1669).
From there, it took a couple of hundred years for people to understand that stuff
(any of the various things around them) was actually made up of different combinations of
a relatively small number of basic (chemical) building blocks.
In 1669, Hennig Brand (as so lavishly illustrated in the painting above by Joseph
Wright) discovered phosphorus. It was the 1st element to be chemically isolated (from urine
as it turns out, which was an important substance in certain industries - I'm not taking the
piss, really). The first form to be isolated was white phosphorus (P4), which glows faintly
upon exposure to oxygen - hence its name, from the Greek φοσφόρος - which in Latin is
Lucifer, the bearer of light - referring to Venus, the morning / evening star.
Looking with hindsight at the whole history of the development of the concept of
elements, one can readily discern 3 phases: the classical; the chemical, and the atomic.
Chronologically speaking, the 1st of these is the classical phase, when people like the
Ancient Greeks, Chinese, Indians and others speculated on the question, what is the
fundamental nature of matter / what are things made of? They thought of this in terms of
things like fire, water, air & earth (for the Greeks), earth, fire, water, wood and metal (for
the Chinese), or earth, water, fire, air & ether (for the Indians). Rather simplistic one
might say, from our modern-day perspective, and somewhat arcane in a way, but in fact it
was a profoundly remarkable departure from what went before: whereas before, people had
talked of supernatural things, and proposed mystical explanations for the origins of matter,
this new approach invoked explanations based on natural things: earth, air and so forth, in
the stead of the emanations of the gods and the like. Furthermore, just think upon it for a
second. Imagine first raising the question (never before asked): is the plurality of the world,
all the myriad things it seems to be made of, really only fundamentally made up of a few
basic things? Is your nose, your dinner plate and the chair you're sitting upon made of just
one or, at most, some few fundamental things? How many people do you think, before
finding out about chemistry, ever wondered what things are made of ultimately in this way?
To me it is remarkable that these people posed the question, let alone that they tried to
answer it somehow. However, I'd like to note one thing here. Of the various cultures which
came up with the early / classical concept of the elements, only one group of cultures, that
which descended from the heritage of the Greeks went from there to eventually developing
a scientific world view.
Source: http://philosophyofscienceportal.blogspot.com/2008/03/edge-of-universe.html
From a 16th century woodcut. Used as a dust jacket cover for Daniel J. Boorstin's The Discoverers.
To me, this was the fundamental step / conceptual leap which took us from
supernaturalism and mysticism eventually towards developing science & the scientific way
of thinking which comes so naturally to many of us today. This however is not to say that
the change came quickly. The classical view held sway for a couple of millennia at least,
until it was replaced by the chemical view, which began roughly with the enlightenment
period and the discovery of phosphorus which I have outlined above, in the 1600s.
Source: http://humanexperience.stanford.edu/supere
A philosopher giving a lecture at the orrery, a painting by Joseph Wright of Derby (1765)
Following this, a variety of other elements were discovered and isolated, though no
one had a fully systematic understanding of the nature of the elements until the work of
Dmitri Meendelev and his predecessors (like Antoine-Laurent de Lavoisier, Stanislao
Cannizzaro, Julius Lothar Meyer, et al).
In 1803, John Dalton used the by then reasonably well understood idea that the
elements combined with each other in definite ratios (as measured by weight) to propose
an atomic theory of matter. He claimed that all the elements were built out of variable
numbers of hydrogen atoms, an idea which, as we shall shortly see, is a bit confusing, but
in a way essentially right. This led him to construct a scale of atomic weights based on the
weight of hydrogen, which was nominally set as being equal to 1.
Source: http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/the-pathto-the-periodic-table/dalton.aspx
John Dalton (1766 - 1844), a teacher for most of his adult life in and around Manchester
By the early 1800s, about 50 elements had been discovered, leading Johann
Wolfgang Dôbereiner to begin arranging the then extant elements into groups with similar
chemical properties. He began doing this in 1817, when he noticed that the atomic weight
of strontium was mid way between those of calcium & barium, and that the 3 elements
shared a number of similar chemical properties. By 1829, he'd noticed that chlorine,
bromine & iodine also shared a number of similar chemical properties, as did lithium,
sodium & potassium.
Source: http://www.iupac.org/publications/ci/2008/3003/si.html
Johann Wolfgang Dôbereiner (1780 - 1849), professor of chemistry at the university of Jena.
Understandably, but mistakenly, he postulated that nature consisted of triads of
elements, within which the middle element had properties in-between those of the other 2.
Later on, other scientists discovered more such triads, but eventually discovered that the
elements could in fact be grouped into sets larger than 3. One of the major stumbling
blocks confounding these early scientists was the poor accuracy of measurement of atomic
weights, which hindered their discovery of more patterns. This speaks directly to the deep
connections betwixt praxis and theory in science, and also explains (to those of you who
may be curious) why Nobel Prizes go to experimenters as well, and not just to theoreticians,
even if, prima facie, it would seem as if theory is what ought to count, as theory is what
provides the conceptual understanding of how the universe works.
Source: http://allperiodictables.com/ClientPages/AAEpages/aaeHistory.html
Alexandre-Émile Béguyer de Chancourtois (1820 - 1886), French geologist & mineralogist.
In 1862, Alexandre-Émile Béguyer de Chancourtois constructed a spiral table, the
1 geometric arrangement of the elements which clearly showed the periodic relationship
between them.
st
Source: http://www.meta-synthesis.com/webbook/35_pt/pt_database.php?PT_id=7 (top Chancourtois's original layout of his Telluric Screw);
http://www.educa.madrid.org/web/ies.isidradeguzman.alcala/departamentos/fisica/temas/sistema
_periodico/introduccion.html (bottom - a more modern version of how it was supposed to work. Once
wound round into a cylinder, the periodic properties became evident, as verticals connected similar
elements together).
This geometric / visual aspect of the table was very important, as it allowed one to
see, quite literally, what the underlying patterns were between the elements. This
representation allowed us to understand something not apparent before, thus illustrating
something important about information: it is not enough just to have it, information must
also be presented in an appropriate manner for it to be productive; this is what leads to
profound insights which may not be discernible otherwise.
In 1863, John Newlands proposed his law of octaves, which contained within it
another fundamental feature of how all chemical behaviour works. Essentially, he noted
that the elements repeated (more-or-less) their chemical behaviour every 8th element. This
was not entirely right, but as we shall shortly see, it was right in a subtle way.
Source: http://d1068036.site.myhosting.com/periodic.f/newlands.html (top - John Alexander Reina
Newlands (1837 - 1898)); http://en.wikipedia.org/wiki/John_Alexander_Reina_Newlands (bottom
- his law of octaves in tabular form as he drew it up it in 1864)
Unfortunately, when he first proposed it, he likened it to the octaves of music and
(perhaps partly because of the legacy of the medieval and much ridiculed idea of the music
of the spheres), this earned him, in no small measure, the ridicule and opprobrium of his
fellow scientists. In fact, it was only after Mendeleev's work, as we shall see, that the
profoundly insightful nature of Newlands' idea became apparent.
Source: http://www.meta-synthesis.com/webbook/35_pt/pt_database.php?PT_id=8
In the 1860s, Lothar Meyer & Dmitri Mendeleev independently produced very
similar versions of the periodic table. In 1864, Meyer wrote a textbook which included an
abbreviated version of his table, and in 1866 he constructed an extended version of it.
Unfortunately for him, he didn't gain any recognition for his work until 1870, a few years
after Mendeleev had published his own version of it in his On the relationship of the
Properties of the Elements to their Atomic Weights, in 1869.
Source: http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/the-pathto-the-periodic-table/meyer-and-mendeleev.aspx (left - Lothar Meyer (1830 - 1895); right - Dmitri
Ivanovich Mendeleev (1834 - 1907))
Valence IV
I line
II
line
III
line
IV
line
V
line
VI
line
Li
Be
The mass
difference
~16
Valence III Valence II Valence I Valence I Valence II
C
N
O
F
Na
Mg
~16
Si
P
S
Cl
K
Ca
~45
As
Se
Br
Rb
Sr
~45
Sn
Sb
Te
I
Cs
Ba
~90
Pb
Bi
Tl
~90
I
II
III
B
Al
C
Si
N
P
O
S
F
Cl
IV
V
Ti
V
Cr
Zr
As
Se
Na
K
Be
Mg
Ca
Nb
Mo
Br
Mn
Fe
Co
Ni
Li
VI
Cu
Zn
VII
In(?
)
Sb
Те
Sr
IX
Tl
Sn
Pb
Ta
Bi
W
I
Ru
Rh
Pd
Rb
VIII
Ag
Cd
Os
Ir
Pt
Cs
Ba
Au
Hg
Source: http://en.wikipedia.org/wiki/Julius_Lothar_Meyer
2 versions of Meyer's table, 1864 & 1870.
Source: http://images-of-elements.com/knowledge.php
Source: https://commons.wikimedia.org/wiki/File:Mendeleev's_1869_periodic_table.png
Mendeleev's 1st draft of his periodic table (above), and a printed version of it (below). Note that even
though Mendeleev was Russian, the chemical symbols were all written in the Roman rather than in
the Cyrillic alphabet.
Now, there is something very important to note here: neither Mendeleev, nor
Meyer had any idea what the nature of atoms might be, and all this work was done long
before the Schrödinger, or even the Rutherford models of the atom were proposed, so no
one knew that atoms had a nucleus, or that this nucleus was 'orbited' by a bunch of
electrons; indeed, no one even knew that there were such things as protons, neutrons and
electrons at this time. Their tables were based purely on the observed periodic properties of
certain seemingly elemental substances. Never-the-less, based on the presence of gaps in his
table, Mendeleev even managed to predict the existence and properties of a number of yet
to be isolated elements.
This was one key to why Mendeleev's table worked: whereas others before him had
tried to organise the then-known-elements, they'd failed to understand that there were
gaps, that in fact many elements had not yet been discovered / isolated. By leaving gaps,
and by following a strictly periodic arrangement, Mendeleev managed to get it essentially
right. The other key was that unlike many of the other scientists of the time, Mendeleev
was not driven by preconceived ideas. He noted that with the lighter elements, periodicity
was found every 8th element, whilst with the heavier ones, it was found every 18th element.
Today, we know why this is the case at the atomic level, but Mendeleev certainly
did not. However, by adhering strictly to what he observed, and by letting the observations
guide his thinking, rather than the other way around, he got it right (more-or-less, and
within the limits of what was then known. In fact it was atomic number, and not atomic
weight which was the significant factor, but a number of other discoveries had to come 1st
before this step could be taken).
As an aside, let me just note that William Odling also constructed a version of the
periodic table, and even managed to get some of the elements into better order than
Mendeleev did, but because of some scandals surrounding Odling's conduct when he was
Secretary of he Chemical Society of London, he failed to secure any recognition for his
work (for more on this, please see: http://en.wikipedia.org/wiki/William_Odling).
Getting back to Mendeleev, because of inaccuracies in the measurements of atomic
weights noted earlier, a number of elements were placed out of order in Mendeleev's table,
but this lacuna notwithstanding, his table was good enough to work with, and to catalyse
the development of modern chemistry.
After the intervening work of a number of other scientists, Henry Moseley entered
the fray in the 19-teens and eventually discovered that it was a quantity called the atomic
number (to be explained shortly), and not the atomic weight which was really important,
and he accordingly rearranged the table according to atomic number, thus paving the way
for Glenn Seaborg to give it its final form.
Source: http://www.aip.org/history/exhibits/rutherford/sections/alpha-particles-atom.html
Henry G J Moseley (1887 - 1915) in the Balliol-Trinity lab in Oxford ca 1910.
Source: http://bancroft.berkeley.edu/CalHistory/chancellor.seaborg.html
Glenn T Seaborg (1912 - 1999) in UC Berkeley, where he worked for much of his life.
Before someone like Moseley could re-organise the periodic table 'properly', you see,
the modern version of the idea that matter was atomic in nature had to be developed 1st.
I shall take that story up in the second part of this post.
End of part I