A radioactive substance decays at a rate of 10% per year. If the initial mass is 500 grams, how much remains after 7 years?

Sun, 03 May 2026 14:44:17 +0000

**How Long Does Radioactive Material Remain After 7 Years? The Science Behind a 10% Annual Decay from 500 Grams** Why are more people turning to simple calculations about radioactive decay these days? It’s not just science—real-life factors like nuclear waste management, medical radiation use, and environmental monitoring are driving curiosity. The steady 10% annual loss in mass due to natural decay mirrors a quiet but significant transformation shaping science communication and public understanding. When starting with 500 grams of a radioactive substance, how much remains after seven years? The answer lies in the predictable rhythm of radioactive decay—stable, measurable, and deeply reliable. **Why Is 10% Annual Decay a Natural Benchmark?**
A 10% yearly decay rate is not arbitrary—it reflects a well-understood process observed in isotopes like carbon-14 and other naturally occurring radioactive materials. In this decay model, each year, 10% of the current mass transforms into different elements, leaving 90% behind. This steady decline is a model data point used across fields such as archaeology, medicine, and environmental science. With an initial mass of 500 grams, the question becomes tangible: how much remains after seven years? This scenario resonates with those tracking long-term material stability or assessing aging processes in scientific contexts. **How Radioactive Decay Works—A Simple Explanation**
Radioactive decay is a statistical process: over time, the number of unstable atoms decreases, and their offspring accumulate. With a 10% annual decay rate, each year’s remaining mass equals 90% of the previous year’s total. This compound decay isn’t instantaneous; it unfolds gradually and reliably. For 500 grams, the formula applies: remaining mass