Question

Zirconium has an atomic number of 40. How many neutrons are there in an isotope of zirconium-92?

Answer 1

In `""^92Zr` there are NECESSARILY `52` neutrons.

Explanation:

The sum of protons and neutrons gives the isotopic mass. For `Zr`, `Z=40` by definition. And thus, `92=40+"number of neutrons"`.

https://en.wikipedia.org/wiki/Zirconium gives details of the individual isotopes. This isotope is about 20% abundant. The most common isotope is `""^90Zr`. How many neutrons does this beast have?