What is the difference between an atom of silver and anatom of gold?

a. one is new and the other is old.

b. their net electrical charges are different.

c. their atomic masses are different.

d. more people would rather have one gold atom than a lot of gold.

The right answer is C. I think, a. and d. are obviously not serious. B is not true, because Ag and Au are in the same group in the periodic table and therefore have the same number of electrons in the last level. So, they form ions with the same charge. C is true beacause Ag and Au have different numbers in the periodic table and different amount of protons and neutrons in their nucleuses.