assume that one particular atom of rhodium (RH) has an atomic mass of 102. why does this number not exactly match the atomic mass of 102.91 listed o the periodic table for this element?

The table below shows the elements that mainly comprise each of the four layers of earth: elements in layers layer main elements crust oxygen, silicon mantle iron, magnesium outer core iron, nickel inner core iron which of these elements make up the layer that is 0.2 to 1.1 percent of earth's total diameter?