How many protons and neutrons are in an atom with this representation:
27 ?
17
which element would have this representation:
43 ?
21
if a neutral atom gains 4 electrons, its charge will be…

Explanation:

There isn't any set number of isotopes an atom can have. As the number of neutrons in an atom increases or decreases, the isotopes tend to become more and more unstable until they get to the point where they decay faster than neutrons can change. According to the International Atomic Energy Agency, Mercury currently has the most at 45 identified isotopes.