Answer: Gold act as cathode.
Explanation:
Standard potential for an electrochemical cell is given by:
= standard electrode potential =
The 
values have to be reduction potentials.
Reduction potentials for given elements
The element Be with negative reduction potential will lose electrons undergo oxidation and thus act as anode.The element Au with positive reduction potential will gain electrons undergo reduction and thus acts as cathode.
Cathode : 
Anode : 
Thus gold act as cathode.
Dark is just absence of light like if the re container a and container b u nee to pour hcl from a to so a has hcl while b has absence of hcl
tell me if u need more examples.hope it helps
Atomic models were developed through indirect observation even though no one had seen an atom. There were many experiments of which I know nothing about, but in the end the scientists managed to come up with a formula and various models to describe atoms.
