Polonium is a heavy element produced exclusively by the r-过程 (rapid neutron capture) during explosive events such as supernovae or neutron star mergers. Due to its radioactive isotopes and relatively short half-lives (the longest, \(^{209}\mathrm{Po}\), has a half-life of only 125.2 years), there is virtually no primordial polonium in the universe. Any polonium present at the formation of the solar system has long since decayed. The polonium found on Earth today is either artificial or results from the 铀和钍的衰变 in natural radioactive chains.
几种钋的同位素作为中间产物出现在四条原始放射性衰变链中：
这些寿命极短的同位素在含铀和钍的矿物中不断产生并消失，构成了天然放射性的一部分。\(^{210}\mathrm{Po}\)（镭F）的半衰期为138.376天，是铀-238衰变链中寿命最长的成员，能够积累到可测量的数量。
\(^{210}\mathrm{Po}\) 在地球科学中被用作天然示踪剂。它由大气中的氡-222（气体）衰变产生，并沉积在陆地与海洋表面。通过与半衰期更长的"母体"\(^{210}\mathrm{Pb}\)（半衰期22.3年）的比值，可用于测定近期海洋沉积物（数百年内）的年代、研究海洋混合过程、生物生产力以及大气中的颗粒物输运。
Polonium was named by its discoverers, 玛丽和皮埃尔·居里, in 1898, in homage to Marie's native 波兰 (then partitioned between the Russian Empire, Austria-Hungary, and Prussia). It was a patriotic and political act, intended to draw attention to the cause of Polish independence, as the country no longer existed on maps. It was the first element named after a country.
在研究沥青铀矿（一种铀矿石）的放射性时，玛丽·居里注意到其放射性强度无法仅用铀含量来解释。她与丈夫皮埃尔承担了数吨矿石化学提纯的艰巨任务。1898年7月，他们宣布发现一种新元素，命名为钋。该元素以其强烈的放射性和与铋的化学相似性为特征。数月后，他们又发现了放射性更强的镭。这些发现为他们赢得了1903年诺贝尔物理学奖（与亨利·贝克勒尔共同获奖）。
由于钋的丰度低且放射性高，分离出可称量的钋极为困难。经过多年矿石处理，才获得微量纯钋盐。1910年首次观测到钋的光谱。直到核反应堆发展后，才实现克级生产。
如今，钋-210主要通过两种人工方式生产：
Global production is very low, on the order of a few hundred grams per year, mainly in 俄罗斯. Its cost is extremely high (hundreds of thousands of dollars per gram for high-purity \(^{210}\mathrm{Po}\)), due to the complexity of its production and separation, and the associated risks.
钋（符号Po，原子序数84）是一种后过渡金属，位于元素周期表第16族（氧族或硫属元素），与氧、硫、硒、碲和����同族。它是该族中唯一在室温下呈金属态的元素。其原子含有84个质子，根据同位素不同，中子数为122至136个。同位素\(^{210}\mathrm{Po}\)含有126个中子。其电子排布为[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁴，具有六个价电子（6s² 6p⁴）。
钋是一种银灰色的软金属，化学性质与其同族元素碲和铋相似。
其强烈的放射性会迅速破坏其晶体结构，并导致自辐照。
Polonium melts at 254°C (527 K) and boils at 962 °C (1235 K). Its decay heat can distort these measurements for macroscopic samples.
从化学性质来看，钋是一种相当活泼的金属，与碲相似。它能溶于酸形成粉红色的Po(IV)溶液，并在空气中易被氧化。钋可形成氧化态为-2、+2、+4和+6的化合物，其中+4价态最为稳定。其化合物通常带有颜色（例如PoCl₄呈黄色，PoBr₄呈红色）。然而，由于其强烈的放射性，研究钋的化学性质极为困难且危险。
Density (α-Po): 9.32 g/cm³.
Melting point: 527 K (254 °C).
Boiling point: 1235 K (962 °C).
Crystal structure (α): Simple cubic (unique among elements).
Electronic configuration: [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁴.
Main oxidation state: +4.
| 同位素 / 符号 | 质子（Z） | 中子（N） | 原子质量（u） | 天然丰度 | 半衰期 / 衰变模式 | 备注/应用 |
|---|---|---|---|---|---|---|
| 钋-208 — \(^{208}\mathrm{Po}\) | 84 | 124 | 207.981246 u | 痕迹（放射成因） | 2.898年（α） | 中寿命同位素，存在于钍系中。可人工生产。 |
| 钋-209 — \(^{209}\mathrm{Po}\) | 84 | 125 | 208.982430 u | 痕迹（放射成因） | 125.2年（α，99.99%；CE，0.001%） | 天然半衰期最长的同位素。主要通过\(^{213}\mathrm{Bi}\)的α衰变产生。 |
| 钋-210 — \(^{210}\mathrm{Po}\) | 84 | 126 | 209.982874 u | 痕量（放射成因） | 138.376天（α） | 最重要且最知名的同位素. Intense alpha radioactivity (5.3 MeV). Used in antistatic sources, thermoelectric generators, and infamously as a poison. Produced from \(^{209}\mathrm{Bi}\) by neutron irradiation. |
注意：:
Electron shells: 电子如何围绕原子核组织.
钋有84个电子，分布在六个电子壳层中。其电子排布为[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁴，第六壳层（s² p⁴）有六个价电子。也可写作：K(2) L(8) M(18) N(32) O(18) P(6)，或完整形式：1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁴。
K层（n=1）: 2 electrons (1s²).
L壳层（n=2）: 8 electrons (2s² 2p⁶).
M层（n=3）: 18 electrons (3s² 3p⁶ 3d¹⁰).
N层（n=4）: 32 electrons (4s² 4p⁶ 4d¹⁰ 4f¹⁴).
O壳层（n=5）: 18 electrons (5s² 5p⁶ 5d¹⁰).
P壳层 (n=6): 6 electrons (6s² 6p⁴).
Polonium has 6 价电子 (6s² 6p⁴). Its chemistry resembles that of tellurium, but with a greater tendency toward lower oxidation states due to the onset of the inert pair effect. The main oxidation states are:
由于处理钋时存在极大危险，其化学性质尚未得到充分探索。
Polonium metal oxidizes rapidly in air to form 二氧化钋 (PoO₂), a yellow solid. When heated in air, it can form mixed oxides.
极少数钋化合物已被制备并详细研究，且始终以微量并在极端谨慎的条件下进行。
When a high-energy alpha particle (such as that from \(^{210}\mathrm{Po}\)) strikes a beryllium-9 nucleus, a nuclear reaction occurs: \(^9\mathrm{Be} + \alpha \rightarrow \,^{12}\mathrm{C} + n\). This reaction produces a neutron. 钋-铍（Po-Be） sources were therefore portable neutron sources, used:
然而，\(^{210}\mathrm{Po}\) 的半衰期较短（138天），使得这些源不实用，需要频繁更换。它们已基本被使用镅-241或锎-252的源所取代。
The intense decay of \(^{210}\mathrm{Po}\) releases a large amount of heat (140 W/g). This heat can be converted into electricity using thermocouples (Seebeck effect). Polonium-210 was used in some of the 首批RTG developed by the Soviets to power equipment in remote locations (beacons, weather stations). However, its short half-life resulted in a rapid decrease in power. For long-duration space missions, it was abandoned in favor of plutonium-238 (half-life 87.7 years).
钋-210是已知毒性最强的物质之一。其危险性源于以下几个因素：
The 半数致死剂量（LD50） for humans by ingestion is estimated at only 1微克（1 µg） of \(^{210}\mathrm{Po}\), or an activity of about 11 GBq.
急性中毒症状（如利特维年科案）在数天后出现，包括：
难以检测: Polonium-210 does not emit significant gamma radiation (only a weak gamma at 803 keV in 0.001% of decays). Direct detection requires a special alpha counter or measurement of radioactivity in excreta (urine, feces). Diagnosis is often delayed.
有限的治疗: There is no specific antidote. Treatment is symptomatic (transfusions, growth factors, antibiotics) and aims to eliminate polonium:
Polonium-210 is naturally present in trace amounts everywhere (soil, water, air) due to decay chains. Higher concentrations are found in uranium ores, phosphate fertilizers (containing uranium), and… 烟草烟雾. Tobacco plants absorb polonium present in soils and fertilizers, and it concentrates in the leaves. Smoking is thus a significant source of internal exposure to \(^{210}\mathrm{Po}\) for smokers.
Due to its extreme toxicity and potential for malicious use, polonium-210 is subject to very strict international controls. It is classified as a 第一类放射性物质 (the most dangerous) by the International Atomic Energy Agency (IAEA). Its trade, transport, and use are closely monitored. Facilities authorized to handle it must comply with exceptionally high nuclear safety and security standards.
含钋废物必须进行包装以确保长期密封，因其半衰期为138天。在适当容器中储存数年后，其放射性活度已显著降低。此类废物随后将按照其他短寿命中放放射性废物的管理方式进行处理。
钋的民用应用如今非常有限且呈下降趋势，已被其他更安全或更实用的放射性同位素（如Am-241、Pu-238、Cf-252）所取代。其主要价值仍在于：
钋将永远与玛丽·居里的天才和勇气，以及其致命毒性的阴险阴影联系在一起。
原子的各种形态：从古代直觉到量子力学 
