Albert's seat has number 13, that I know, but he weighs... (insert rummaging sounds from the direction of the knowledge tag)
26.982, it seems.
Clark and Albert sat at the same old table they'd met at years ago.
The periodic table
As per usual, there was hardly anything to drink
Out of the 118 known elements, only Bromine and Mercury are liquid in NTP
and they'd had nothing but sips between them.
Si, P, S, as in Silicon, Phosphorus, and Sulphur, the elements 14,15 and 16.
Near Albert, there were some scraps of bacon, and an egg, scrambled.
Elements 5 to 8 (one row up) are B,C,N,O. One row down, there's Zn,Ga,Ge, which scrambles to "an egg".
It was the same order as always.
There were a couple of new cyborgs sitting at the far end of the table though, several superheavy artificial elements were officially accepted recently.
After this lazy breakfast, the question, of course, is:
How much does Albert weigh?
Albert is "Al", or Aluminum (13). Aluminum’s atomic mass is given as 26.982.
And Clark then? Well, I missed two thirds of the explanation myself, but as OP helpfully pointed out in the comments below,
Clark is Chlorine (17), Argon (18) and Potassium (19), or Cl,Ar,K for short.
Oh, if only I could upvote a question twice!
Post-Solve OP Edit:
@Bass answered this riddle perfectly! The context of his answer can be seen here: