what is the heaviest element that has only one isotope and is not radioactive?

To find the heaviest element that has only one stable isotope and is not radioactive, we can utilize the Periodic Table of Elements.

1. First, we need to narrow down our search to the elements that have only one stable isotope. Stable isotopes do not decay over time, so we are looking for an element with no radioactive isotopes. Referencing the periodic table, we can identify elements that have a single, non-zero natural abundance value for their isotopes.

2. Now, let's focus on the heaviest elements. Starting from the top of the periodic table, elements become progressively heavier. We need to find one among them that satisfies the criteria mentioned earlier.

3. As we move down the periodic table, we find that elements such as hydrogen, helium, and lithium do not satisfy the criterion of having only one stable isotope.

4. However, when we reach the element Bismuth (Bi) at atomic number 83, we observe that it does have only one stable isotope, which is Bismuth-209. This isotope of bismuth does not undergo radioactive decay.

Therefore, Bismuth (Bi) is the heaviest element that has only one isotope and is not radioactive.