If 2 g of element x combine with 7 g of element y to form compound xy how many grams of y are needed to form compound xy2

You use the atomic number to find out how many protons and neutrons there are in the atom. you use the atomic mass to find out how many protons and electrons there are in the atom. 

The answers are 3.c kelvin4.b liquids only

Do you have any options for this question?

Answer(28.02g/mol);