Reading Wikipedia, I came across a notion that I don’t think I’d come across before: chemically explosive elements. The example I came across was antimony, an allotrope of which can detonate to form the most stable metallic allotrope. I’m not aware of any other chemically explosive elements, but maybe there are others I’m not aware of. I suppose organic compounds containing only carbon atoms might present other examples.

Interesting. I hadn’t heard of that one before.
From http://en.wikipedia.org/wiki/Antimony#Properties

A rare explosive form of antimony can be formed from the electrolysis of antimony trichloride. When scratched with a sharp implement, an exothermic reaction occurs and white fumes are given off as metallic antimony is formed; when rubbed with a pestle in a mortar, a strong detonation occurs.

The only thing I can think of that’s vaguely similar is tin.
From http://en.wikipedia.org/wiki/Tin_pest

Tin pest is an autocatalytic, allotropic transformation of the element tin, which causes deterioration of tin objects at low temperatures. Tin pest has also been called tin disease, tin blight or tin leprosy (Lèpre d’étain).

It was observed in medieval Europe that the pipes of church pipe organs were affected in cool climates. As soon as the tin began decomposing, the process accelerated.

…

At 13.2 degrees Celsius (about 56 degrees Fahrenheit) and below, pure tin transforms from the silvery, ductile metallic allotrope of β-form white tin to brittle, nonmetallic, α-form grey tin with a diamond structure. The transformation is slow to initiate due to a high activation energy but the presence of germanium (or crystal structures of similar form and size) or very low temperatures ~-30 degrees Celsius aids the initiation. There is also a large volume increase of about 27% associated with the phase change. Eventually the α-form decomposes into powder, hence the name tin pest.

The decomposition will catalyze itself, which is why the reaction speeds up once it starts; the mere presence of tin pest leads to more tin pest. Tin objects at low temperatures will simply disintegrate.

This transformation isn’t exactly explosive, though. I guess you could make it a little more spectacular by building a tin structure that contained a compressed spring, OTOH, tin bends very easily, so I don’t imagine that a pure tin spring could be compressed very much without becoming permanently deformed. :)

wouldn’t some nuclear weapons come under this heading as well?

Zinc whiskers can cause small explosions, just not in the zinc; normally finds a nice bit of delicate electronics to flash over.

wookiemeister said:

wouldn’t some nuclear weapons come under this heading as well?

No, because they aren’t chemically explosive elements.

Chemical reactions are electromagnetic in nature, but nuclear reactions involve the strong and weak nuclear forces.

i’m reading that a chemical reaction involves electrons in the shells

a nuclear reaction occurs in the nucleus

wookiemeister said:

i’m reading that a chemical reaction involves electrons in the shells

a nuclear reaction occurs in the nucleus

Yeah. And only the electrons in the outer shells are involved in chemical bonding.

Some nuclear reactions emit electrons (aka beta particles). For example, if a neutron turns into a proton the nucleus will emit an electron (and an anti-neutrino), but those electrons generally have considerably kinetic energy, so they’re unlikely to be captured by the parent atom. OTOH, sometimes the reverse reaction occurs: the nucleus absorbs an electron and converts a proton into a neutron, and in some cases the absorbed electron comes from an inner orbital of the atom.

But even though these reactions involve electrons, they are not considered to be chemical in nature.

PM 2Ring said:

Yeah. And only the electrons in the outer shells are involved in chemical bonding.

My yr 12 chem teacher gave us a default answer for exams when we had NFI – ‘outer shell electrons’. It explains pretty much all of units 3 and 4 chem…

PM 2Ring said:

wookiemeister said:

wouldn’t some nuclear weapons come under this heading as well?

No, because they aren’t chemically explosive elements.

And this is precisely why I explicitly said chemically explosive elements. Note also that we are excluding highly air-sensitive elements such as white phosphorus.

One normally doesn’t think of elements as being explosive because what are they going to form? The answer is that they are a highly unstable allotrope that forms a much more stable allotrope. I mentioned organic compounds containing only carbon atoms because organic chemistry does provide a rich source of chemical structures, many of which are highly unstable. But nitrogen is also a potential source for explosive elements quite simply because such structures will be quite unstable with respect to dinitrogen. Looking at Wikipedia, two hypothetical structures caught my attention:

hexazine

and octaazacubane

The latter compound, though it has yet to be synthesised, is predicted to have a detonation velocity that is 48.5% faster than the fastest known nonnuclear explosive.

KJW said:

PM 2Ring said:

wookiemeister said:

wouldn’t some nuclear weapons come under this heading as well?

No, because they aren’t chemically explosive elements.

And this is precisely why I explicitly said chemically explosive elements. Note also that we are excluding highly air-sensitive elements such as white phosphorus.

One normally doesn’t think of elements as being explosive because what are they going to form? The answer is that they are a highly unstable allotrope that forms a much more stable allotrope. I mentioned organic compounds containing only carbon atoms because organic chemistry does provide a rich source of chemical structures, many of which are highly unstable. But nitrogen is also a potential source for explosive elements quite simply because such structures will be quite unstable with respect to dinitrogen. Looking at Wikipedia, two hypothetical structures caught my attention:

hexazine

and octaazacubane

The latter compound, though it has yet to be synthesised, is predicted to have a detonation velocity that is 48.5% faster than the fastest known nonnuclear explosive.

So you’d also exclude water sensitive Sodium?

KJW said:

The latter compound, though it has yet to be synthesised, is predicted to have a detonation velocity that is 48.5% faster than the fastest known nonnuclear explosive.

I bet the queue for people wanting to try synthesising that isn’t too long.

roughbarked said:

KJW said:

PM 2Ring said:

No, because they aren’t chemically explosive elements.

And this is precisely why I explicitly said chemically explosive elements. Note also that we are excluding highly air-sensitive elements such as white phosphorus.

One normally doesn’t think of elements as being explosive because what are they going to form? The answer is that they are a highly unstable allotrope that forms a much more stable allotrope. I mentioned organic compounds containing only carbon atoms because organic chemistry does provide a rich source of chemical structures, many of which are highly unstable. But nitrogen is also a potential source for explosive elements quite simply because such structures will be quite unstable with respect to dinitrogen. Looking at Wikipedia, two hypothetical structures caught my attention:

hexazine

and octaazacubane

The latter compound, though it has yet to be synthesised, is predicted to have a detonation velocity that is 48.5% faster than the fastest known nonnuclear explosive.

So you’d also exclude water sensitive Sodium?

Yes. Reactive elements are commonplace.

KJW said:

roughbarked said:

KJW said:

And this is precisely why I explicitly said chemically explosive elements. Note also that we are excluding highly air-sensitive elements such as white phosphorus.

One normally doesn’t think of elements as being explosive because what are they going to form? The answer is that they are a highly unstable allotrope that forms a much more stable allotrope. I mentioned organic compounds containing only carbon atoms because organic chemistry does provide a rich source of chemical structures, many of which are highly unstable. But nitrogen is also a potential source for explosive elements quite simply because such structures will be quite unstable with respect to dinitrogen. Looking at Wikipedia, two hypothetical structures caught my attention:

hexazine

and octaazacubane

The latter compound, though it has yet to be synthesised, is predicted to have a detonation velocity that is 48.5% faster than the fastest known nonnuclear explosive.

So you’d also exclude water sensitive Sodium?

Yes. Reactive elements are commonplace.

Nitrogen is reactive, is it not?

roughbarked said:

Nitrogen is reactive, is it not?

Dinitrogen is very unreactive.

KJW said:

roughbarked said:

Nitrogen is reactive, is it not?

Dinitrogen is very unreactive.

Keep up the plainspeak.. ;)

It just occurred to me that I had forgotten about ozone (an explosive allotrope of oxygen).

KJW said:

It just occurred to me that I had forgotten about ozone (an explosive allotrope of oxygen).

oxygen was next off my lips but I waited.

if you could make nitrogen rings and other rings of non metallic elements then you could create explosives from elements that might normally have three possible bondings?

how stable they would be is another matter I guess

Bunch of O radicals would be very explosive.

Gunpowder was the second explosive invented, I don’t know what the first one was, anyway brisance is what did it for gunpowder, too low a brisance compared to modern explosives.

Gunpowder still has its uses…