The activity of radioactive isotopes do not change with change in — Nuclear Chemistry and Radioactivity Chemistry Question

💡 Solution & Explanation

Step 1 - Key Principle: Nuclear Nature of Radioactivity Radioactivity is governed by the **nuclear decay constant** $\lambda$, which reflects only the intrinsic stability of the nucleus. Therefore, the activity $A = \lambda N$ depends on: 1. The decay constant $\lambda$ — a nuclear property, unaffected by external conditions. 2. The number of radioactive atoms $N$ — which CAN change with time or the amount present. Step 2 - Evaluate Each Factor **(A) Temperature**: Nuclear forces are $\sim10^6$ times stronger than chemical forces. Even extremely high temperatures (thousands of K) cannot affect nuclear binding. $\lambda$ is independent of temperature. Activity per gram is **independent** of temperature. ✓ **(B) Pressure**: External pressure acts only on the electron cloud, not on nuclei at $10^{-15}$ m scale. $\lambda$ is independent of pressure. Activity per gram is **independent** of pressure. ✓ **(C) Chemical environment**: Whether the atom is in elemental form, in a compound, in solution, or ionized, only the electron configuration changes. The nucleus is unaffected. Activity per gram is **independent** of chemical environment. ✓ **(D) Amount**: Activity $A = \lambda N$. If the amount (i.e., $N$) changes, the total activity $A$ changes proportionally. So activity **does depend on** the amount present. ✗ Step 3 - Conclusion Radioactive activity does NOT change with temperature, pressure, or chemical environment, but it DOES change with the amount (number of radioactive atoms). $$\boxed{\text{Answer: A, B, C}}$$