Respuesta :
Answer:
They are averages.
Explanation:
atomic numbers on periodic tables are derived from the average value of all the isotopes of the element. So being averages they are sometimes not integers.
Answer:
The sum of the number of protons and neutrons in an atom is called the mass number. Atomic mass is never an integer number for several reasons: The atomic mass reported on a periodic table is the weighted average of all the naturally occurring isotopes. Being an average it would be most unlikely to be a whole number.
Explanation: