8FUNCTIONS: element - CYANA function

Synopsis: element(<integer>) = <integer>

Ordinal number (number of protons in the nucleus) of the atom with
index <integer>, e.g., 1 for hydrogen, 6 for carbon, 7 for nitrogen,
8 for oxygen and 16 for sulfur atoms.

Optionally, the <integer> atom index can be replaced by a string
consisting of the atom name and the residue number, separated by a
blank or a period, '.'.
