Caesium (Cs)

General Information

• Symbol: Cs
• Atomic Number: 55
• Atomic Weight: 132.90545196 u
• Element Category: Alkali metal
• Group: 1
• Period: 6
• Block: s-block

Physical Properties

• Appearance: Silvery-gold metallic
• Density: 1.93 g/cm³
• Melting Point: 28.5 °C (83.3 °F)
• Boiling Point: 671 °C (1240 °F)
• Phase at STP: Solid (liquid at slightly above room temperature)
• Electron Configuration: [Xe] 6s¹
• Oxidation States: +1 (most common)

Chemical Properties

• Reactivity: Extremely reactive, especially with water and air. It ignites spontaneously in air and reacts explosively with water.
• Compounds: Forms compounds such as caesium chloride (CsCl), caesium nitrate (CsNO₃), and caesium carbonate (Cs₂CO₃).

Uses and Applications

• Atomic Clocks: Used in the most accurate atomic clocks, which are the standard for timekeeping.
• Oil Drilling: Used in drilling fluids for oil and gas wells due to its high density.
• Electronics: Employed in photoelectric cells and vacuum tubes.
• Medical Imaging: Caesium-137 is used in radiotherapy for cancer treatment and in industrial gauges.
• Chemistry: Used as a catalyst in various chemical reactions and in the production of certain types of glass.

Occurrence and Extraction

• Natural Occurrence: Found primarily in the mineral pollucite (CsAlSi₂O₆) and in lepidolite.
• Extraction: Extracted from pollucite through processes involving acid digestion and precipitation.

Isotopes

• Stable Isotope: Caesium-133
• Radioactive Isotopes: Caesium-137 (used in medical and industrial applications) and Caesium-134 (used in nuclear medicine)

Safety and Handling

• Hazards: Highly reactive and flammable; caesium must be handled with care to prevent reactions with water or air. Caesium compounds, especially caesium-137, are highly radioactive and toxic.
• Precautions: Store under inert conditions, such as in mineral oil or in a vacuum-sealed container. Use protective equipment when handling caesium and its compounds.

History

• Discovery: Discovered by Robert Bunsen and Gustav Kirchhoff in 1860 through the analysis of mineral water using flame spectroscopy.
• Name Origin: Derived from the Latin word “caesius,” meaning sky blue, due to the bright blue lines in its emission spectrum.

Additional Facts

• Crystal Structure: Body-centered cubic (bcc)
• Magnetic Properties: Paramagnetic
• Thermal Conductivity: Moderate, about 35.9 W/m·K
• Electrical Resistivity: About 20.5 nΩ·m at room temperature

Summary

Caesium is an extremely reactive alkali metal with significant applications in atomic clocks, oil drilling, electronics, and medical imaging. It is found primarily in the mineral pollucite and is extracted through acid digestion and precipitation. Due to its high reactivity and the radioactivity of some of its isotopes, caesium must be handled with great care.

40 Question and Answer Pairs About Caesium

1. What is the atomic number of Caesium?

   • 55

2. What is the symbol for Caesium?

   • Cs

3. What is the atomic weight of Caesium?

   • 132.90545196 u

4. In which group of the periodic table is Caesium found?

   • Group 1

5. What period is Caesium in?

   • Period 6

6. What block does Caesium belong to?

   • s-block

7. What is the melting point of Caesium?

   • 28.5 °C (83.3 °F)

8. What is the boiling point of Caesium?

   • 671 °C (1240 °F)

9. What is the density of Caesium?

   • 1.93 g/cm³

10. What is the electron configuration of Caesium?

    • [Xe] 6s¹

11. What is the common oxidation state of Caesium?

    • +1

12. What is the appearance of Caesium?

    • Silvery-gold metallic

13. Is Caesium reactive with air?

    • Yes, it ignites spontaneously in air.

14. Name a compound of Caesium.

    • Caesium chloride (CsCl)

15. What is a common use of Caesium in timekeeping?

    • Used in atomic clocks.

16. How is Caesium used in oil drilling?

    • In drilling fluids for oil and gas wells due to its high density.

17. What role does Caesium play in electronics?

    • Employed in photoelectric cells and vacuum tubes.

18. How is Caesium-137 used in medicine?

    • In radiotherapy for cancer treatment.

19. What application does Caesium have in chemistry?

    • Used as a catalyst in various chemical reactions.

20. Name a mineral that contains Caesium.

    • Pollucite (CsAlSi₂O₆)

21. How is Caesium extracted from pollucite?

    • Through acid digestion and precipitation.

22. What is the most stable isotope of Caesium?

    • Caesium-133

23. Name a radioactive isotope of Caesium used in industrial applications.

    • Caesium-137

24. What safety hazard is associated with Caesium?

    • Highly reactive and flammable.

25. How should Caesium be stored?

    • Under inert conditions, such as in mineral oil or in a vacuum-sealed container.

26. Who discovered Caesium?

    • Robert Bunsen and Gustav Kirchhoff

27. Where does the name Caesium come from?

    • From the Latin word “caesius,” meaning sky blue.

28. What is the crystal structure of Caesium?

    • Body-centered cubic (bcc)

29. Is Caesium paramagnetic or diamagnetic?

    • Paramagnetic

30. What is the thermal conductivity of Caesium?

    • About 35.9 W/m·K

31. What is the electrical resistivity of Caesium at room temperature?

    • About 20.5 nΩ·m

32. What is the primary oxidation state of Caesium?

    • +1

33. Is Caesium found as a free element in nature?

    • No, it is found in minerals like pollucite.

34. What is the common name of caesium nitrate?

    • CsNO₃

35. What is a major application of caesium carbonate (Cs₂CO₃)?

    • Used in organic synthesis and as a base in chemical reactions.

36. How does Caesium benefit atomic clocks?

    • Provides extremely accurate timekeeping.

37. What is the boiling point of Caesium in Kelvin?

    • 944 K

38. What group does Caesium belong to in the periodic table?

    • Alkali metals

39. What is the natural abundance of Caesium-133?

    • Nearly 100%

40. Can Caesium be used in high-temperature applications?

    • Yes, but it requires careful handling due to its reactivity.