Which element has no stable isotopes?

1. (subscript)27 Co
2. (subscript)51 Sb
3. (subscript)90 Th
4. (subscript)82 Pb

I believe it's either 2 or 3, but I can't decide which. I'm not sure how to go about answering this question, how can you tell which have stable isotopes and which don't?

The elements mentioned on the list have 0,1,2 and 4 stable isotopes, but NOT in order.

You only have to browse through articles on stable isotopes to find out which one you need. For example, Google "stable isotope", the Wiki article provides a complete list.

The answer will also explain why we don't see compounds of that element in the chemistry lab. Unstable isotopes are radioactive!

http://en.wikipedia.org/wiki/Stable_isotope

To determine which element has no stable isotopes among the given options, you can examine the periodic table and the known isotopes of each element.

First, let's understand what stable isotopes are. Isotopes are variants of an element that have differing numbers of neutrons in their atomic nuclei. Some isotopes are stable, meaning they do not undergo radioactive decay over time, while others are unstable and eventually decay into other elements.

To find the stable isotopes, you can use a periodic table that lists the atomic mass of each element. The atomic mass represents the weighted average of all the isotopes of an element found in nature.

Now, let's analyze each option:

1. (subscript)27 Co: Cobalt-59 (59Co) and Cobalt-61 (61Co) are the two stable isotopes of cobalt. Therefore, option 1 has stable isotopes.

2. (subscript)51 Sb: Antimony has two stable isotopes: Antimony-121 (121Sb) and Antimony-123 (123Sb). Therefore, option 2 also has stable isotopes.

3. (subscript)90 Th: Thorium has one naturally occurring isotope, Thorium-232 (232Th). Based on this information, the third option may be the correct one, as it seems to have only one stable isotope.

4. (subscript)82 Pb: Lead has four stable isotopes: Lead-204 (204Pb), Lead-206 (206Pb), Lead-207 (207Pb), and Lead-208 (208Pb). Hence, option 4 has stable isotopes as well.

From this analysis, we can conclude that the correct answer is option 3, (subscript)90 Th, as it has no stable isotopes.

Personally, I think this is a very poor question; however, here is a chart.

http://en.wikipedia.org/wiki/Isotope_table_(divided)