Subject: Do all elements on the periodic table have isotopes

Most people say all elements have isotopes because atomic masses are decimal
numbers, but protons don't have a mass of exactly 1 amu, and one book mentioned
that when protons and neutrons combine in a nucleus, some mass is lost as
binding energy according to E=mc^2.  My favourite chem book by Zumdahl only
mentions a few elements with isotopes.  I'm trying to teach isotopes to my Y10
class, and would like to know if there is a definitive answer with proper reasons.

Re: Do all elements on the periodic table have isotopes