| A ____ atom has one proton and zero neutrons. |
carbon-14 |
| Radioactive ____ has a half-life of about 4 days. |
deuterium (H-2) |
| A stable isotope of hydrogen with one neutron is ____. |
phosphorus-32 |
| Radioactive ____ has a half-life of about 24,000 years. |
plutonium-239 |
| Radioactive ____ has a half-life of about 1.2 billion years. |
potassium-40 |
| Radioactive ____ has a half-life of about 14 days. |
protium (H-1) |
| Radioactive ____ has a half-life of about 5,730 years. |
radon-222 |
| Radioactive ____ has a half-life of about 4.5 billion years. |
uranium-238 |
