The protons and neutrons are located in the nucleus of an atom, while the electrons are located in the orbital cloud. <span />
To calculate the average mass of the element, we take the summation of the product of the isotope and the percent abundance. We calculate as follows:
Average atomic mass = .374 ( 184.953 amu ) + .626 ( <span>186.958 amu ) = 186.208 amu
Hope this answers the question. Have a nice day.</span>
