碳-14 测年法为什么能确定古物年代？
Why can carbon-14 dating determine the age of ancient objects?
活体生物不断与环境交换碳，体内碳-14 与稳定碳比例恒定；死亡后交换停止，碳-14 按已知半衰期衰变减少。测出现存碳-14 比例即可反推死亡至今的时间，有效范围约数万年。该方法由利比创立并获诺贝尔化学奖。
Living organisms constantly exchange carbon, keeping a constant C-14 to stable-carbon ratio; after death exchange stops and C-14 decays at its known half-life. Measuring the remaining C-14 fraction back-calculates the time since death, valid up to tens of thousands of years. Libby developed it and won the Nobel Prize in Chemistry.
难度 进阶 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Housecroft & Sharpe,《Inorganic Chemistry》第5版,Pearson,2018
C. E. Housecroft and A. G. Sharpe, Inorganic Chemistry, 5th ed., Pearson, 2018
#碳-14测年 #半衰期 #利比
什么是放射性？哪些原子核不稳定？
What is radioactivity and which nuclei are unstable?
放射性是某些原子核自发放出 α、β 或 γ 射线并转变为其他核素的现象。中子数与质子数比例失衡（过多或过少）或质量数过大的核往往不稳定，如铀-238、碳-14。衰变使核趋向更稳定的中子/质子比。
Radioactivity is the spontaneous emission of α, β, or γ radiation as a nucleus changes into another nuclide. Nuclei with imbalanced neutron-to-proton ratios or very large mass numbers are often unstable, like uranium-238 and carbon-14. Decay drives the nucleus toward a more stable ratio.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Housecroft & Sharpe,《Inorganic Chemistry》第5版,Pearson,2018
C. E. Housecroft and A. G. Sharpe, Inorganic Chemistry, 5th ed., Pearson, 2018
#放射性 #α衰变 #不稳定核
核裂变和核聚变有什么不同？
How do nuclear fission and fusion differ?
核裂变是重核（如铀-235）分裂成两个中等质量核并释放能量，是现有核电站的基础。核聚变是轻核（如氢的同位素）结合成较重核并释放更多能量，是太阳和氢弹的能量来源，目前受控聚变仍在攻关。两者都依质量亏损转化为能。
Nuclear fission splits a heavy nucleus (e.g., uranium-235) into medium ones, releasing energy and underpinning today's reactors. Fusion joins light nuclei (e.g., hydrogen isotopes) into heavier ones, releasing even more energy—the source of the Sun and hydrogen bombs; controlled fusion is still being developed. Both convert mass defect into energy.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Housecroft & Sharpe,《Inorganic Chemistry》第5版,Pearson,2018
C. E. Housecroft and A. G. Sharpe, Inorganic Chemistry, 5th ed., Pearson, 2018
#核裂变 #核聚变 #质量亏损
放射性同位素的半衰期是什么？
What is the half-life of a radioactive isotope?
半衰期是放射性核素衰变掉一半所需的时间，是该核素的固有常数，不受温度、压力或化学状态影响。碳-14 半衰期约 5730 年，常用于考古测年；碘-131 半衰期约 8 天，用于甲状腺治疗。半衰期越长，放射性越持久。
Half-life is the time for half of a radioactive nuclide to decay; it is an intrinsic constant unaffected by temperature, pressure, or chemical state. Carbon-14's half-life is about 5730 years, used in archaeological dating; iodine-131's is about 8 days, used for thyroid treatment. Longer half-life means more persistent radioactivity.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Housecroft & Sharpe,《Inorganic Chemistry》第5版,Pearson,2018
C. E. Housecroft and A. G. Sharpe, Inorganic Chemistry, 5th ed., Pearson, 2018
#半衰期 #碳-14 #考古测年