Sciencemadness Discussion Board

Why is Beryllium so rare ?

metalresearcher - 10-8-2023 at 10:55

Being the fourth element in the periodic table, it one of the rarest elements, particularly so low in the periodic table. Its neighbors are much more abundant, even the relatively rare lithium. And it is an even element, normally even elements are more abundant than odd elements, like its (odd) neighbors 3 Li and 5 B.

In stars, where all the elements are created by nucleosynthesis, He fusion does not deliver Be as Be-8 (two He-4 nuclei fused together) because it is extremely unstable. It rather fuses to C-12.

Why is this ?

phlogiston - 10-8-2023 at 12:12

I think you've already described the main reason: Be-8 is unstable. As to why -that- is: probably because it can decay in not just one, but two alpha particles, which are very stable. so, that is an energetically favourable reaction.

Admagistr - 10-8-2023 at 12:49

The naturally stable beryllium found in minerals and gems is Be-9.But I read in a book by Dr.Josiph Kleczek, who was a famous astronomer and astrophysicist, that not only Be-8 is unstable but also Be-9 decays rapidly at the very high temperatures found in stars and I think the main decay product is two helium nuclei.

violet sin - 10-8-2023 at 14:53

Tellurium is rare because of a hydride off gassing during the hot planetary formation IIRC. I wonder if beryllium has a similar cause.


Wikipedia tellurium
"Its extreme rarity in the Earth's crust, comparable to that of platinum, is due partly to its formation of a volatile hydride that caused tellurium to be lost to space as a gas during the hot nebular formation of Earth"

Admagistr - 10-8-2023 at 15:03

Quote: Originally posted by violet sin  
Tellurium is rare because of a hydride off gassing during the hot planetary formation IIRC. I wonder if beryllium has a similar cause.


Wikipedia tellurium
"Its extreme rarity in the Earth's crust, comparable to that of platinum, is due partly to its formation of a volatile hydride that caused tellurium to be lost to space as a gas during the hot nebular formation of Earth"


BeO is volatile at temperatures above 1000 C in the presence of water vapour, which is how it escaped from the magma in the depths of the earth and formed beryl deposits on the earth's surface in the environment of granite pegmatites. If BeO did not have the property of concentrating in pegmatites in this way,beryllium would be much less available.Its rarity is similar to that of tin.If hot water steam were to leave the earth's atmosphere under supervolcanism,a significant amount of beryllium could escape in this way...

clearly_not_atara - 10-8-2023 at 19:07

Basically, nucleons have orbitals like electrons. The first orbital has two states, just like with electrons. So helium-4, with 2 and 2, is unusually stable for a small nucleus. Normally, more nucleons = more stable up to about iron, but beryllium has half its nucleons in the higher kinetic energy state and that just tips it into instability. Beryllium-8 decays by alpha decay; the next alpha-decay nucleus is tellurium-104!

The orbital numbers for nucleons are not quite the same as electrons, due to complicated symmetry in quantum chromodynamics. The first orbital has two, then six, then twelve, then eight (!?!?!), then 22... due to relativistic weirdness and non-convergence of QCD diagrams we can't actually predict the whole series.

https://en.wikipedia.org/wiki/Magic_number_(physics)

[Edited on 11-8-2023 by clearly_not_atara]

Σldritch - 10-8-2023 at 19:41

More than the scarcity of Beryllium, the scarcity of Beryllium-7 bothers me. If the isotope were stable, which it is so alluringly close to being, the metallic element could be had in a 22% lighter form - and it is already the lightest structurally useful metal!

[Edited on 11-8-2023 by Σldritch]

woelen - 12-8-2023 at 14:32

It is scarce, because it is formed in stars, but also quickly is destroyed again. In stellar cores, there is fusion of light elements, and beryllium is one of the elements, formed in that process, especially in older stars, in which further fusion of helium cores is an important source of its energy output. But under the conditions in such stellar cores, with helium present in large amounts, it easily is fused further with helium nuclei to form carbon. So, upon formation, it quickly is reacted further with helium nuclei to make carbon. Carbon on the other hand, does not as easily fuse with other nuclei, and for this reason, carbon is much more abundant than beryllium. It is this situation, which makes our presence posisble :D