Perfect — now onto **Astatine (At, atomic number 85).**
⚠️ Astatine is the **rarest naturally occurring halogen**. Only about **25 grams** exist in the entire Earth’s crust at any moment. It cannot be mined or concentrated — all usable astatine is **artificially synthesized** in nuclear facilities.
Here are the **20 most common methods of extracting Astatine** (really: methods of *producing* and *isolating* it):
---
# **20 Most Common Methods of Extracting Astatine**
### **A. Historical / Natural Sources**
1. **Trace Recovery from Uranium Ores** – Vanishingly small amounts (not practical).
2. **Chemical Co-precipitation with Halogens** – Early Curie-style attempts, not scalable.
---
### **B. Accelerator-Based Production (Main Modern Method)**
3. **Bombardment of Bismuth-209 with Alpha Particles** – ^209Bi(α,2n)^211At (the standard method).
4. **Cyclotron Irradiation of Lead Targets** – Alternative accelerator route.
5. **Proton Bombardment of Thorium/Uranium** – Produces trace astatine isotopes.
6. **Spallation of Heavy Nuclei with Protons** – Yields astatine among many isotopes.
7. **High-Energy Photonuclear Reactions (γ,n)** – Creates astatine in very small yields.
8. **Bremsstrahlung Photoproduction** – Using high-energy photons on Bi or Pb targets.
9. **Neutron Capture in Certain Heavy Elements** – Rare, indirect isotope production.
---
### **C. Radiochemical Separation Techniques**
10. **Dry Distillation of Irradiated Bismuth Targets** – Volatilizes astatine for capture.
11. **Wet Chemical Dissolution (Acid Leaching of Bi Targets)** – Common in radiochemistry labs.
12. **Solvent Extraction (Organic Phase Separation)** – Isolates astatine from Bi solutions.
13. **Ion Exchange Chromatography** – Separates At from other fission products.
14. **Electrodeposition onto Noble Metals (Au, Pt, Ag)** – Collects astatine isotopes.
15. **Co-precipitation with Halide Salts (Iodide/Chloride)** – Mimics iodine’s chemistry.
16. **Sublimation under Inert Atmosphere** – Transfers volatile astatine compounds.
17. **Vacuum Distillation** – Alternative purification of At isotopes.
---
### **D. Advanced & Medical Isolation Methods**
18. **Dry-Wet Hybrid Separation (Distillation + Solvent Extraction)** – Optimizes yield for medical use.
19. **Microfluidic Radiochemistry Platforms** – Miniaturized systems for ^211At labeling in radiopharmaceuticals.
20. **Automated Target Dissolution & Extraction Systems** – Modern hospital/medical isotope labs for cancer therapy.
---
✅ **Summary:**
* **Natural sources** are negligible.
* **Accelerator production** (Bi-209 + α → ^211At) is the **primary practical method** worldwide.
* **Separation & purification** rely on distillation, solvent extraction, and electrochemical methods.
* **Applications**: mainly in **targeted alpha-particle cancer therapy** (^211At is a promising isotope).
---
Next in order is **Radon (Rn, atomic number 86).**
Would you like me to continue with the **20 most common methods of extracting Radon**?
