Pique the Geek 20120415: Beryllium, a Very Unusual Element

(9 pm. – promoted by ek hornbeck)

Beryllium, atomic number (Z) 4, is the second metallic element in the periodic table.  By looking at the periodic table, one would think that it would be very similar to magnesium and calcium, but one would be wrong on several accounts.  There shall be more about that later.

Beryllium is a comparatively rare element, both on earth and in the cosmos.  There are a couple of reasons for that as well, and again there will be more about that later.

Most people have never seen the pure metal, but most of us have seen compounds of it, at least in jewelry stores, because it is an essential component of real emeralds.  Let us take a look at this little know element and see what good it is, and any ill that it might cause.

At first glance, looking at the fact that beryllium-8 “looks’ like two extremely stable helium nuclei bonded together, one would think that this isotope would be extremely stable.  In fact, the opposite is true.  Helium nuclei are so much more stable by themselves that Be-8 falls apart into two helium nuclei with a half life of only 6.7 x 10^-17 seconds!  The only stable isotope is Be-9, so this makes beryllium unique as being the only element with a even Z with a single stable isotope with an odd mass number.  All other monoisotopic elements have an odd Z.  Quantum physics can be strange indeed!

The stable isotope, Be-9, is sensitive to alpha bombardment, producing a neutron and an atom of carbon-12.  This means that it is quite rare in hydrogen burning stars, because as soon as it forms a helium nucleus “zaps” it.  Now, that process is not very efficient, only around, as I recall, only about 30 times out of a million, but there are so many alpha particles that the reaction is essentially complete.  Remember, an alpha particle is nothing but a fast moving helium nucleus.

So, whence comes Be-9?  Mostly from cosmic ray interaction with cosmic debris.  That explains why such a light element is so rare.

So, one might ask, what good is this comparatively rare element?  That is quite a good question, and mostly has to do with its unique combination of physical and chemical properties.  For one thing, it is light, only half again as dense as water.  It is also quite stiff.  Those two properties make it quite useful for certain acoustic applications, because the speed of sound in beryllium is very, very fast.  At normal temperature and pressure, the speed of sound in beryllium is 12,900 m/s.  Compare this to air (343 m/s), water (1,484 m/s), and even steel (5,120 m/s).

This property makes is quite useful for high range loudspeakers (tweeters), but the cost and other disadvantages limit its use there to quite expensive home or professional systems.

Due to its position in the periodic table, one would expect it to resemble magnesium and calcium in most of its properties, but as just pointed out, it has some unique properties.  Actually, this normal.  The first member of a family often has properties unlike the other members.  Hydrogen takes it to the extreme by being the only gaseous member of the alkali metal series!  This is because the first members of the series are much smaller, less massive, and have more strongly attracted outer electrons than subsequent members.

There are no medical uses for beryllium.  It is quite toxic.  We shall cover that in some depth later.

The largest use for beryllium is in the electronics field.  It turns out that it is very transparent to X-rays, and very short wavelength X-rays are used in the photolithographic production of integrated circuits.  It is also widely used in the medical field for X-ray windows.

The widest application for beryllium is in the aerospace field.  Because of its lightness, stiffness, and high thermal conductivity, it it unmatched for a number of applications including airframes.  It appears that some of the applications are military secrets, but known uses include satellites and missiles.

The element is now used extensively for mirrors where its stiffness and lightness are important.  Some optical systems use very fast moving mirrors, and beryllium is ideal for this application.  For use at near ambient temperatures it is usually plated with nickel (nickel is easier to polish).  For space applications it is used bare because the nickel plating would flake off of it.

Most of us have never seem pure beryllium, but many of us have seen a rather common allow of beryllium (about 2%) and copper.  This allow is used for nonsparking tools used in explosive environments.  Copper and brass are much too soft to make useful wrenches, screwdrivers, and the like, but the small amount of beryllium hardens the copper to a remarkable degree.

One compound of beryllium that almost everyone has seen is emerald.  It is a beryllium aluminum silicate, Be₃Al₂(SiO₃)₆, colored green be either chromium or vanadium impurities.  In the US both colorants are accepted, but in much of the rest of the world emeralds colored with vanadium have to have a qualifier and can not be marketed simply as emeralds.  Here is a very nice natural crystal:

In interesting fairly recent application for beryllium, in the form of the oxide, is to mix a little with uranium oxide in nuclear reactor fuel pellets to increase the rate of heat conduction.  This helps to dissipate heat in the rods faster, making them less apt to melt during off normal conditions such as when coolant water is interrupted.  Beryllium oxide combines the properties of excellent electrical insulation and excellent thermal conductivity, two properties not often seen together in a solid.  Thus is is often used for heat sinks for high power radio transmitters.  The only other material that comes to mind that combines these properties is diamond.

Beryllium has two distinct disadvantages.  First, it is EXPENSIVE.  It costs several hundred dollars per pound, due to scarcity, difficulty in refining, and difficulty in fabrication.

The major disadvantage is the extreme toxicity of beryllium.  Solid pieces of the metal are not particularly dangerous, but any form of beryllium or its salts that become dusts are an extreme hazard.  If inhaled, sometimes in extremely low amounts, pulmonary berylliosis can result, and it can be life threatening.  It has been known for some time that beryllium dusts are harmful, and the situation came to a head in the US in the later 1940s when beryllium zinc silicate was being used as a phosphor for fluorescent lamps.  Many people became ill and shortly thereafter beryllium salts were removed from this use.  Modern lamps do not use beryllium at all.

Skin contact with beryllium dusts can cause painful lesions, called granulomas, that are slow to heal.  This is especially prone to happen where the skin has been damaged previously.

There are now analytical methods to detect beryllium in the workplace that assure that concentrations are far below the OSHA standards, but good industrial hygiene is still essential when working with the material.  In addition the condition mentioned above, all beryllium compounds are considered to be known human carcinogens.

Interestingly, the original name for beryllium was glucinium in reference to the sweet taste of its soluble salts!  Fortunately, beryllium is not well absorbed from the digestive system, but lots of early chemists became ill or died from pulling stunts like that.

Well, you have done it again!  You have wasted many more perfectly good einsteins of photons reading this.  And even though Britt Hume realizes that there is more pressure on Iran behind the scenes to curtail its nuclear program that he admits when he reads me say it, I always learn much more than I could possibly hope to teach by writing this series.  Thus, keep those comments, questions, corrections, and other feedback coming!  Tips and recs are also always welcome.  I shall remain here tonight as long as comments warrant, and shall return tomorrow around 9:00 PM Eastern for Review Time.

My wrist continues to improve, but it it surely taking a long time.  I gain a little functionality every day, most noticeable during my tonsorial routine.  I can shave almost my whole face with my right hand now, and it is the splint that makes it difficult to get to the left side.  I still can not write very much, and The Girl promised to help me fill out my tax forms and write the check tonight or tomorrow.  If I am away from responding to comments for a while, you know why.

Warmest regards,

Doc, aka Dr. David W. Smith

Crossposted at

The Stars Hollow Gazette,

Daily Kos, and

firefly-dreaming