Two oxides of copper can occur; CuO and Cu2O. You heat a 1.51g of a sample of each of these in the absence of air and isolate 1.21 g of Cu. Which copper oxide did the Cu come from and how many moles of the sample did you start with?

☆ionisation energy increases across a period from na -> ar☆ionisation energy decreases down a group from li -> fr☆ionic radius decreases across a period from na -> cl☆ionic radius increases down a groupfrom f -> ii hope it clarifies your doubts

Sorry i dont understand the question can you rephase it?

The correct answer is weight.