New Scientist
An elementary history lesson






13 August 2013 by Andrea Sella
Book information
A Tale of Seven Elements by Eric Scerri
Published by: Oxford University Press
Price: $19.95
What makes the idea remarkable? It was a way of organising elements in the absence of
any theory (Image: Theodore Gray/Visuals Unlimited/Corbis
In A Tale of Seven Elements, Eric Scerri reveals the remarkable human stories that explain
how we filled the gaps in the periodic table
TO CHEMISTS, the periodic table is the cornerstone that supports so much of our discipline.
But it also has much wider appeal, illustrated by the proliferation of amusing periodic tables
of such things as vegetables, furniture or cyclists. And there are T-shirts with element
symbols spelling words like Be Er and C Ho Co La Te.
In the mind of the chemist, though, the periodic table is overlain with the heuristics we use
daily to rationalise chemical behaviour. The brainchild of Dmitri Mendeleev is remarkable
because it was conceived as an empirical tool, a way to organise elements according to
their properties in the absence of any theory.
The periodic table was built in 1869, 30 years before the discovery of the electron, 40 years
before Ernest Rutherford discovered the atomic nucleus and 50 years before quantum
mechanics showed the onion-like structure of the layers of electrons that orbit the nucleus.
But it was British chemist Henry Moseley at the start of the 20th century who provided the
crucial insight into why the elements were ordered according to the charge on the nucleus
rather than by mass. In so doing, he put precise limits on how many elements remained
undiscovered. That he was killed aged 27 during the first world war created one of science's
great might-have-been stories.
I
In recent years, there have been many books about the elements, either encyclopedic
surveys, or quirkier and more readable companions. Now we have a very different
offering: A Tale of Seven Elements by Eric Scerri, one of the foremost authorities on the
history of the periodic table.
This is the remarkable story of the seven elements still "missing" from the periodic table by
the early 20th century and how they were found. I knew the history of three of them:
technetium, hafnium and rhenium. But I had always passed over the other four: francium,
astatine, promethium and protactinium.
Scerri has tremendous human stories to tell, but what emerges strongly is the struggle to sift
real discoveries from claims and counterclaims, with overbearing egos, national pride, errors
and misunderstandings all adding to the fun.
Given that our scientific heroes always triumph in the end, we are blissfully unaware of how
their forgotten contemporaries had alternative proposals and data to present. With hindsight,
it is easy to laugh at the elements now consigned to the scrapheap of science,
like anglohelvetium, which would have taken astatine's place, had its "discoverers" actually
found the element 85 they were looking for. In the thick of the chase, confusion reigned.
Scerri tells these stories well. He reminds us that not all of Mendeleev's predictions were
correct, and he highlights the important role that discovering elements plays in
understanding both the quantum theory of electrons and the nucleus. The crucial work of
physicist Lise Meitner in the discovery of protactinium while her research partner Otto Hahn
was fighting in the first world war is also brought to life wonderfully through their letters.
Yet Scerri is not a natural popular science writer – his language seldom soars beyond the
descriptive. The cut and thrust of the debate is meticulously footnoted, but we do not have a
sense of who the people were and their motivations.
There are also surprising omissions. For example, Scerri does not discuss the 2009 North
American shortage of technetium, which is used in millions of medical diagnostic procedures
each year. The element's main source, the Canadian reactor at Chalk River, remained
closed for much longer than expected after a leak. The availability of radioisotopes is still a
serious issue.
Yet despite the quibbles, this is a brilliant book about the interface of chemistry and physics.
Above all, the stories argue powerfully for curiosity-driven research, and show how hard it is
to see the wood for the trees in the thick of a scientific battle. They are powerful reminders,
too, that the scientific method always allows the truth to shine through, you just have to be
patient.
This article appeared in print under the headline "There's hafnium..."
Andrea Sella is a chemist at University College London