Final answer:
The listed nuclei are supposed to be outside the band of stability. However, Nitrogen-14 and Calcium-40 are both stable isotopes. Phosphorus-30 is likely to undergo beta decay, and Chromium-50 would decay by double beta decay.
Step-by-step explanation:
Nuclei that do not lie within the band of stability are unstable and tend to decay to reach a more stable state. The types of radioactive decay depend primarily on the ratio of neutrons to protons within the nucleus, and which side of the stability band the nuclide lies on.
- Nitrogen-14 (14/7N) is actually a stable isotope and does not decay. It mistakenly appears on the list;
- Phosphorus-30 (30/15P) has too many neutrons compared to protons and is likely to undergo beta decay to convert a neutron into a proton, forming sulfur-30;
- Calcium-40 (40/20Ca) is actually stable for all practical purposes and is the most abundant isotope of calcium in nature;
- Chromium-50 (50/24Cr) would undergo double beta decay due to having a relatively high neutron to proton ratio.
Nuclei above the band of stability typically decay by positron emission or electron capture, while those below decay by beta emission. However, in this specific question, it appears that there is confusion, as some of the listed isotopes are in fact stable.