Well, first off, if you want some sort of realism in aliens, neon is a
bit unlikely.
Here's a quick rundown on chemistry possibilities for near-terrestrial planets:
nitrogen compound breathers (forms various acids in solution, which can
function to oxidize food. Also, one of the NO compounds is paramagnetic.
The effects of that, who knows, but perhaps the atmosphere itself will
produce a magnetic field.)
sulphur compound breathers (sulphur is very similar to oxygen, except
that it is solid at near-earth temperatures. H2S is a possible
substitution for the role water has in plants, and is indeed used that
way in certain ocean-vent life forms on Earth. However, sulphur isn't as
reactive as oxygen, so life forms might be lower energy <ie- move slower
to catch food, sustain energy with greater care, etc>)
Chlorine/flourine/etc breathers (HIGHLY reactive, so life forms may be
more energetic.)
Other chemistries:
Silicon- silicon forms VERY tight bonds, so either used in high
temperature life form (ie- molten rock level) or used for skeletal-type
structures.
Sugar- this is our chemistry (more or less) Note: at high temperatures,
sugars are as explosive as nitrates are in our temperature.
Nitrates- Cold life forms, possibly.
Ammonia- at low temperatures, ammonia bears some of the same
dissasociative properties as water.
Metallic- Possible electron transfers and salt solutions form basic chemistry.
Inert gas foo- certain inert gases can be used in gas pump lasers.
Perhaps a 'gas cloud' being, composed of many separate pieces, uses
lasers to interconnect the nodes... or something.
Heavy metals, radioactives- depending on the chemical type of the
compounds, oxidation may or may not be important. Radioactive decay and
linked reactions form chemistry. Note: Xenon absorbs neutrons, and may
be of use in such a life form.
Crystalline- As WHAT crystal hasn't been mentioned, there's alot of
lattitude here. Crystals have interesting properties of resonance and
reproduction that may make it more common than non-crystalline life.
<shrug>
Cold hydrogen- mentioned in a certain Carl Sagan book whose title eludes
me, liquid hydrogen can occur in two forms, determined by whether the
spins of the electrons match or not. He postulates that this difference
may be utilizable and be the structure of some sort of life form.
Plasma- the photospheres of stars may be the most abundant sources of
life in the cosmos. Plasmas, ionized gas, are matter and energy which
affect each other. It doesn't take a huge leap to postulate life of this
sort.
Well, this covers some of the possibilities for chemistry in life forms.
When I'm up to it, I'll post about some of the different forms I think
life could take. Oh, and maybe the social/evolution stuff (though that
is so specific perhaps I shouldn't...)
Until next time...
- - -The Incoherent Will