The half-life of a radioactive substance is 6 years. How much of a 100g sample remains after 18 years?

Sun, 03 May 2026 20:31:47 +0000

**Why the half-life of a radioactive substance is 6 years—So much of a 100g sample vanishes after 18 years?**
Recent conversations across science forums, educational platforms, and media outlets reflect growing public interest in foundational nuclear physics concepts—especially the predictable decay of radioactive materials. The half-life of a radioactive substance is 6 years. This simple fact sparks curiosity about how much of a substance remains long after its initial quantity. For example, after 18 years—equivalent to exactly three half-lives—what starts as a 100-gram sample transforms predictably. Understanding this process helps people grasp real-world applications in medicine, environmental safety, and energy. While the concept may seem technical, it plays an essential role shaping trust in science and informed decision-making. The half-life of a radioactive substance is 6 years. This means that every 6-year period, the material’s radioactivity cuts in half. After 18 years—spanning three such cycles—the original 100 grams decays through multiple stages. Starting at 100g, the first 6 years leave 50g, the next 6 years reduce it to 25g, and after the final 6, only 12.5 grams remain. This predictable decay creates a measurable timeline, making radioactive substances reliable tools in medicine, archaeology, and industrial applications. The concept’s clarity supports its rising relevance in both education and public dialogue. Across the United States, interest in radioactive half-life concepts is rising alongside demand for accurate scientific information. With increasing focus on nuclear medicine, nuclear power safety, and environmental monitoring, understanding how long a substance remains effective or manageable is more pertinent than ever. Communities exploring energy sources, medical diagnostics, or radiation safety need reliable data—not speculation. The predictable decay model offers that clarity, reinforcing public confidence in science-backed systems and policies. How exactly does the half-life of a radioactive substance is 6 years actually dictate this decay? At each half-life, half of the material’s unstable atoms transform into a different element through radioactive decay. This process follows an exponential pattern, not linear, resulting in gradually diminishing quantities. Mathematically, the remaining mass after *n* half-lives equals the original mass divided by 2 raised to *n*. For a 6-year half-life and 18 years total, three half-lives mean 100g becomes 100 ÷ (2³) = 100 ÷ 8 = 12.5 grams. This formula underpins accurate predictions used in regulated industries and research alike.