Hydrogen has 1 unstable isotope, and 2 stable isotopes.
Unstable isotopes can be chemically reactive.
all but one.
Not all isotopes are unstable. But now more than 3 000 unstable isotopes are known, artificial or natural.
In a neutral hydrogen atom, there is one electron, regardless of the isotope.
Copper has natural isotopes of 63,67. And other isotopes are known at least from 58 through 70. But these are unstable.
3
Polonium is the element in group 16 that has unstable isotopes. It is a radioactive element with no stable isotopes.
Some isotopes are stable, others are unstable.
All the isotopes of californium are radioactive, artificial and unstable.
Isotopes of hydrogen are Hydrogen-1 (protium), ‎Hydrogen-2 (deuterium), ‎and Hydrogen-3 (tritium).
All the isotopes of americium are radioactive and unstable.
These isotopes are unstable and emit radiation.