What is the fraction of the hydrogen atom's mass (Ā¹H) that is in the nucleus? The mass of a proton is 1.007276 u, and the mass of the Ā¹H atom is 1.007825 u. Express your answer using four significant figures. What is the fraction of the hydrogen atom's volume that is occupied by the nucleus? The Bohr radius is 0.529Ć10ā»Ā¹ā°m. Express your answer using two significant figures.