Zr 94: half life 1,1.1017 years, double beta decay Zr 96: half life 2,0.1019 years, double beta decay
Zirconium does have radioactive isotopes, but the main ones used in industry are not radioactive.
No, there are many stable isotopes.
Not all of the transition elements are radioactive. Many of them are, and some of them have common radioactive isotopes, but some of them have no naturally occurring radioactive isotopes. Please note that all elements have synthetic radioactive isotopes, at least.
Not all isotopes are radioactive; the radioactive isotopes are unstable and emit radiations.
Both isotopes and radioactive isotopes are pretty much the same but radioactive isotopes are better because it can be used to make medicine.
Today are known approx. 3 000 radioactive isotopes, natural or artificial.
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All of them.
Sodium has no radioactive isotopes.
Radioactive isotopes are not stable.
The number of neutrons for any given element varies, depending on the isotopes. Search the Wikipedia, or Google, for "Isotopes of Zirconium" for the isotopes of this particular element. The list of isotopes will give you the atomic mass (protons + neutrons) for the different isotopes; subtract the atomic number (which is the number of protons) to get the number of neutrons for each isotope.
All the uranium isotopes are radioactive.