sometimes I think of it as a very
pedestrian element it's something that
doesn't have very many applications so
it's quite easy to overlook but at the
same time some of those applications are
actually really important so you have to
remember that like a lot of elements in
the periodic table it can be very easily
overlooked but actually it's got some
really fantastic uses when I think of
the
elementum I think of the English word
hobble which may sound a bit funny but
it's because there's a simple way of
remembering the names of all the
lanthanide Rare Earth elements let me
show you it begins with
lanum and goes languid Centos praise
Ned's
promise of you put that in small
European garden
tubs dinosaurs Hubble ically thrumming
yellow loots so there it is number 67
hium which you remember through the word
hobble which begins with the same
letters ho o I learned this I think when
I was at school it's really great I can
write the whole row of lanthanide
elements on the Blackboard or white
board nowadays and the students say Wow
and think I'm a genius holum was first
observed not sort of isolated but
observed
spectroscopically uh by two Chemists in
1878 one of them was called Mark de
Fontaine and the other was called jacis
Lis sé they saw this wonderful spectrum
and they thought this must be something
new and different they obviously great
PR guys because they called it element X
I don't know much aboutum except it's
named after Stockholm or the Latin name
for Stockholm I know also that there was
a lot of argument when the element was
was first discovered who discovered it
had they discovered it had they not they
had actually seen it in it it's its uh
clean isolated state but it wasn't until
a year later that it was actually
isolated properly for the first time and
of course one of the issues like with
many of the lanthanides is actually
isolating holum on its own because many
of the lanthanides are of a very similar
size so you dig them out of the ground
in minerals all jumbled up together and
you have to separate them out so you can
put all the thulium in one pile over
there and all the helium in one pile
over there and this is quite difficult
to do but eventually people have figured
out how to do it the other thing I know
aboutum is that at low temperature it
exhibits very strong
magnetism it's not much use at room
temperature but because of the number of
electrons unpaired electrons at low
temperature you can get very strong
magnetic effects so a year later in 187
9 a guy called Pierre tdor CLE manages
to separate holmium on its own for the
first time and he decided to call it uh
after the Latin for Holier which is
actually Stockholm which is his native
City the electrons have a whole series
of different energy levels depending
whether they're paired or unpaired and
the energy separation between these
levels is not very great so as you warm
it up the electrons have more energy so
some of them go into a higher state if
you cool it right down they will go into
the Lower State which in this case
happens to be the really magnetic one so
holmium has some very interesting
fluorescence phenomena um so you might
be able to find some kind of application
where you need something that fluoresces
with a particular type of color one sort
of spin-off from that is that it and
we're back to this uh nature of the
absorption spectrum that our two folk
found many many years ago that spectrum
is very distinct and it almost never
changes
the strange arrangement of electrons
means that if you put some in glass you
can get quite an elaborate spectrum and
we used to use homei filters to
calibrate our spectrometers where
basically you would do a run with the
holmium sample and check that the
spectrometer is calibrated properly so
that when you record a real Spectrum you
know that the Peaks are actually in the
right place we've searched everywhere in
the lab but we don't calibrate
spectrometers anymore so we can't find
the filter I thought all elements had a
really distinctive Spectrum are you
saying that elements spectrums are not
reliable they can do I mean the first
thing is it depends what type of
spectroscopy you're actually running
because there are many many different
types then the second part is um an
element on its own will have a very
distinctive Spectrum but also most
elements don't turn up in the world or
are not found in the world just as the
element on their own I mean obviously
gold often is which is why it's used
often in jewelry but most metals in the
periodic table are dug out of the ground
in the form of oxides or you want to
turn them into an interesting molecule
to do something with them and usually
when you're changing that environment
around the metal you're changing its
core electronic structure which then
means its spectroscopy will be different
but the lanthanides generally although
there are exceptions to the rule they're
not really interested in what's going on
around them and in fact one thing I
often teach our undergraduates is that
whilst transition metals change a lot
depending on what's immediately bonded
to the metal lanthanides by and large
are sort of screened away from what's
going on around them and so you can make
a really impressive so fancy molecule
with holum in the middle of it and you
could record its uh ultraviolet visible
electronic spectrum and it would look
barely any different to the free iron in
the gas phase because as far as it's
concerned it's no different it's almost
like the lanthanides are really
antisocial and they don't want to talk
to molecules that bond to them in the
way the transition metals do it is used
in surgical lasers where you dope a
small amount of helium into so-call yag
yum aluminium garnet and then you get
laser emission around about 2 microns
that's 2 millionths of a meter and that
wavelength is particularly good because
it's strongly absorbed by water which
your flesh contains a lot of water so
surgeons can cut very precisely with the
laser and apparently the laser is also
so-called self poter rizing so that when
you cut through a blood vessel it tends
to seal the blood vessel off so the
patient doesn't pour blood which is
obviously useful holmium uh is one of
the elements in the periodic table that
obeys the Odo Harin rule the auto Harkin
rule says that elements with even atomic
numbers are more prevalent than those
with odd it just so happens that holum
is an element with an odd atomic number
and therefore it's less prevalent than
its neighbors which have even numbers in
general what you would is that the
heavier the element gets the less of it
there should be but what you see is if
you drew a line it's not a nice smooth
line it keeps on going up and down up
and down even though the line overall is
decreasing and so what this basically
shows is that the even numbered Atomic
nuclei are on average more abundant than
their neighbors which doesn't sort of
make sense at first until you think
about how are elements actually formed
now you start off with hydrogen in the
universe in Suns and that's converted
into helium and it's usually helium
nuclei being pushed together that help
you form heavier and heavier elements
but once you start with an even numbered
nuclei then your products are always
going to be even so like carbon which is
six would be three helium nuclei to get
to nitrogen which is seven then you need
to add in a hydrogen from somewhere and
that seems to be a little bit more
difficult to do because most of the
hydrogen had to be used to be turned
into helium so once you go into a
universe with helium you're more likely
to get even numbered elements one though
that is the big outlier is still
actually hydrogen and of course that's a
good job cuz if it hadn't then you
wouldn't have water which is essential
for life and you wouldn't have most of
the molecules in the world which do tend
to be quite hydrogen Rich yeah so holum
obeys the rule because if you look at
its nearest neighbors of dysprosium and
herum there's more of them than there is
holmium so you can see there's a
definite dip in between those two even
numbered elements I don't know I think
it's not so much it's
forgettable but you don't remember it
which is rather forgettable sort of
means that you think about it and then
you forget about it I would say you most
people never really think about it so I
did say homman was a little bit
pedestrian but there's another uh fact
that I've dug up about it as well which
is in nuclear processes uh you want to
be able to control all of those neutrons
flying around otherwise things would get
out of control and uh the element that
normally gets the uh the Limelight where
that's concerned is boron it's really
good at absorbing but a little known
fact as the holmium is actually quite
good at absorbing neutrons as well so
you can kind of use it as a sacrificial
element to keep your nuclear reactions
under control I
suppose one of the things that people
have said and there's an article in the
latest issue of this journal Nature
chemistry and they have an article
about they have an article aboutum with
a rather um catchy title
helyum in which the important part of
this article says that they think that
helium is the most underused element
nobody has really found a good use for
it I'm not sure I think there may be
other elements that would be a strong
Contender for this title but we should
let them have their
say the other thing aboutum which I
think is important is that it has a
pretty prominent position on this
tie so whoever designed this tie clearly
thought that homean was
important so perhaps they've got a good
application