[cliffhanley]

do elements become more rare the further up the periodic table we go?  is helium rarer than hydrogen?  lithium rarer than helium?  uranium rarer than proactinium?  etc etc?

[Arkcon]

I think if you search the internet, you'll see the general trend you refer to is fuzzy at best.  There are 3 big reasons for the general trend.  One involves the synthesis of elements, so there's a Google point for you.  Another involves distribution, and selective observation, spatially.  Again, distribution of elements is a good Google point for you.  Then, there's another, selectivity to the observation, following another variable, which people tend to forget, often even as they go deeply into science.  What is the biggest source of error in any observation?

[cliffhanley]

cheers again arkcon.

accordin to wiki, the most abundant elements, in order, are; H He O C Ne Fe N Si Mg S

as for,

"what is the biggest source of error in any observation?"

i'll get back to you when i've had a wee think

[Arkcon]

cheers again arkcon.

accordin to wiki, the most abundant elements, in order, are; H He

Well, what do those two scream at you?

O C

  Some mechanism is concentrating those?

Ne Fe N Si Mg S

except for two, what do they have in common?

as for,

"what is the biggest source of error in any observation?"

i'll get back to you when i've had a wee think

I check a mirror every morning.