const char *OEGetAtomicSymbol(unsigned int elemno)
Returns the atomic symbol associated with the specified atomic number.
This function returns a valid pointer to a NUL-character,
elemno is neither greater than zero nor less than the symbolic constant
OEElemNo::MAXELEM. Otherwise, all returned values
are NUL-terminated, with the first character uppercase, and the second
character either a NUL or lowercase (in which case the third character is
always the NUL-terminator).