The correct answer is 13.Concept:Atomic Number: It is the number of protons or electrons present in the atom.Mass number: It is the number of protons and neutrons taken together of an atom.It is measured in the atomic mass unit, amu or simply 'u'.An element is represented in the following manner:Explanation:Mass of 1 He atom = 4 u4u He has atoms = 11u He will have atoms = 1/452u He will have atoms = 52/4 = 13The Number of atoms in 13 moles = 13À” 6.022À”1023 = 7.8286 À” 1024.Therefore 52 u of He has 7.8286 À” 1024 = 78.286 À” 1023 atoms.