Subject: Why is the relative atomic mass of an element never a whole number

I am getting confused with info to answer this question - I think that it is 
because an element contains different isotopes and they have all got rounded 
masses on the periodic table, so when these are added together and then divided 
to give an average for the relative atomic mass it can not be a whole number.  
But I am not confident that thi is right.

Re: Why is the relative atomic mass of an element never a whole number