Compute the mass in grams of a sample of copper containing 12 atoms

Silver tarnishes as silver metal reacts with hydrogen sulfide, h2s, in the air. in this reaction, dark silver sulfide, au2s, covers the surface of silver. when silver is polished, this coating of silver sulfide can be removed from the surface. this makes the silver shiny again. enter the coefficients that balance the tarnishing reaction equation. (type 1 for no coefficient.)

Which statement best describes the flow of energy in this scenario

What is the correct lewis dot structure for arsenic?