What is the relationship between natural abundance and stability?
The correct answer and explanation is:
Correct Answer:
There is a direct relationship between natural abundance and stability — the more stable an isotope is, the higher its natural abundance tends to be.
300-Word Explanation:
Natural abundance refers to the relative proportion of a particular isotope of an element found in nature. Stability, in this context, refers to the nucleus of an atom remaining unchanged over time — that is, not undergoing radioactive decay. A strong relationship exists between these two properties: stable isotopes are more abundant in nature, while unstable (radioactive) isotopes are found in much lower quantities or may not occur naturally at all.
Atoms consist of protons and neutrons in the nucleus. The stability of a nucleus depends largely on the ratio of neutrons to protons. A balance in this ratio leads to greater nuclear stability. Stable isotopes, which have this balance, do not decay over time and thus accumulate in nature, making their relative abundance higher. For example, carbon has two stable isotopes: carbon-12 (about 98.9% abundant) and carbon-13 (about 1.1%). These dominate because they are stable. In contrast, carbon-14 is radioactive and occurs in trace amounts (~0.0000000001%) due to continuous formation in the atmosphere.
Unstable isotopes decay into more stable forms over time, often emitting radiation. Since they break down, their presence in nature diminishes unless continuously replenished (e.g., by cosmic rays or nuclear reactions). Because of their short half-lives, most unstable isotopes are either rare or entirely absent from natural sources.
Thus, the greater the stability of an isotope, the longer it can persist in the environment, leading to a higher natural abundance. Conversely, isotopes that are highly unstable decay quickly and are found only in small amounts or must be artificially created in laboratories.
In summary, stability leads to higher natural abundance, and the two are fundamentally linked in nuclear chemistry.