Re: Monatomic hydrogen as fuel - need a low bond energy to single hydrogen atoms.

rgregoryclark@xxxxxxxxx wrote:
Atomic hydrogen or monatomic (or monoatomic) hydrogen fuel isn't a
type of nuclear engine. The terminology just means the hydrogen occurs
as single atoms rather than the usual H2 seen in hydrogen gas. The
specific impulse (ISP) of this fuel could be as high as 1500 s. The big
problem with this fuel is keeping it stable against it's recombining
into H2 when stored in its monatomic form. This still hasn't been
solved:

Use of Atomic Fuels for Rocket-Powered Launch Vehicles Analyzed.
http://www.grc.nasa.gov/WWW/RT1998/5000/5830palaszewski.html

Current research is focused in storing it as individual atoms within
cryogenic liquid helium.
However, arcjet engines or arcjet torches that use hydrogen as the
fuel can produce monatomic hydrogen by high electrical power. High
power or temperature is needed to break the hydrogen bond of H2, at a
bond energy of about 104 kcal/mol.
Are there molecules with bonds of hydrogen at much lower bond
energies?
I thought of molecules that specifically had the type of bonds known
in biochemistry as "hydrogen bonds". These are, in most cases, weaker
than covalent bonds. However, the only cases I've seen had an H atom
attached to another atom by a "hydrogen bond" but that H atom was also
attached to a second atom by a covalent bond. "Hydrogen bonds" always
have the H between two other atoms but is it possible for both of these
bonds to be of the "hydrogen bond" type?
According to this page hydrogen iodide, HI, with a bond energy of 71
kcal/mole can be decomposed into H and I by uv light at a wavelength of
266 nm:

Chem 32 Virtual Manual.
http://kalee.tock.com/chem32/the2/26s.html

Are there other gases where a single hydrogen atom can be dissociated
at a lower energy?


Bob Clark


I'm not sure where to begin... I would suggest electronegativity would be the most useful.

then review lewis diagrams, resonance, conjugation, and VSEPR...

You don't even need to cover molecular orbital theory to account for why hydrogen bonds occur the way they do, and not some other way.

If you have hydrogen floating around, chances are it is going to be positively charged. It will attempt to balance the charge problem ASAP. This sort of thing will take precedence over hydrogen bonding which will only occur when the hydrogen is part of a molecule,"sharing" electrons with another atom which tends to dominate the sharing such that the relative positive charge of the portion of the molecule where the hydrogen resides is accessible to other atoms/molecules in the nearby proximity.

Think about hydrogen bonds as attraction, and not bonding.

or don't, its up to you.

.

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