[Chimera-users] how could u know the order of atoms?

Dear Sir/Madam, I am using Chimera viewer..and it is a great viewer ever... I kindly have a question... how could you know (from PDB file) the coorect bonding between atoms? I mean that how could you know that this atom is connected with CA not N nor C.....do u have all these bonds stored already in a database? or you use atom positions to determine that? I appreciate your time.... Kamal