Gold (Au)

General Information

• Symbol: Au
• Atomic Number: 79
• Atomic Weight: 196.966569 u
• Element Category: Transition metal
• Group: 11
• Period: 6
• Block: d-block

Physical Properties

• Appearance: Yellow metallic
• Density: 19.32 g/cm³
• Melting Point: 1064 °C (1947 °F)
• Boiling Point: 2970 °C (5378 °F)
• Phase at STP: Solid
• Electron Configuration: [Xe] 4f¹⁴ 5d¹⁰ 6s¹
• Oxidation States: +3 (most common), +1

Chemical Properties

• Reactivity: Gold is one of the least reactive chemical elements. It is resistant to corrosion and tarnishing. It does not react with oxygen or sulfur but can be dissolved in aqua regia (a mixture of hydrochloric and nitric acid) and in cyanide solutions.
• Compounds: Forms compounds such as gold chloride (AuCl₃), gold cyanide (Au(CN)₂⁻), and gold oxide (Au₂O₃).

Uses and Applications

• Jewelry: Highly valued for its aesthetic appeal and resistance to tarnish, making it a popular choice for jewelry.
• Electronics: Used in electronics for connectors, switches, and relay contacts due to its excellent conductivity and resistance to corrosion.
• Finance: Employed as a standard for currency and as an investment in the form of coins and bullion.
• Dentistry: Used in dental alloys for crowns and bridges due to its biocompatibility and resistance to corrosion.
• Medicine: Applied in medical treatments, including as a drug to treat rheumatoid arthritis and in certain diagnostic procedures.
• Aerospace: Used in reflective coatings for satellites and spacecraft due to its infrared reflectivity and thermal properties.

Occurrence and Extraction

• Natural Occurrence: Found in its native form in rocks, veins, and alluvial deposits. Often occurs in association with quartz and sulfide minerals.
• Extraction: Extracted through mining methods such as placer mining, panning, sluicing, dredging, and hard rock mining. It is then purified using processes like cyanidation, amalgamation, and electrolysis.

Isotopes

• Stable Isotopes: Gold has one stable isotope: Gold-197.
• Radioactive Isotopes: Several radioactive isotopes, including Gold-198, used in medical applications and scientific research.

Safety and Handling

• Hazards: Gold is non-toxic and non-irritating. However, some gold compounds can be toxic and should be handled with care.
• Precautions: Handle gold compounds with appropriate protective equipment to avoid inhalation or ingestion.

History

• Discovery: Known to ancient civilizations; its use dates back to at least 2600 BCE.
• Name Origin: Derived from the Old English word “geolu,” meaning yellow. Its symbol “Au” comes from the Latin word “aurum,” meaning shining dawn.

Additional Facts

• Crystal Structure: Face-centered cubic (fcc)
• Magnetic Properties: Diamagnetic
• Thermal Conductivity: High, about 318 W/m·K
• Electrical Resistivity: Low, about 22.14 nΩ·m at room temperature

Summary

Gold is a highly valued transition metal known for its aesthetic appeal, resistance to tarnish, and excellent conductivity. It has significant applications in jewelry, electronics, finance, dentistry, medicine, and aerospace. Found in its native form in various geological settings, gold is extracted through mining and purified using chemical processes. Its historical significance and unique properties make it a valuable element in various fields.

40 Question and Answer Pairs About Gold

1. What is the atomic number of Gold?

   • 79

2. What is the symbol for Gold?

   • Au

3. What is the atomic weight of Gold?

   • 196.966569 u

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

   • Group 11

5. What period is Gold in?

   • Period 6

6. What block does Gold belong to?

   • d-block

7. What is the melting point of Gold?

   • 1064 °C (1947 °F)

8. What is the boiling point of Gold?

   • 2970 °C (5378 °F)

9. What is the density of Gold?

   • 19.32 g/cm³

10. What is the electron configuration of Gold?

    • [Xe] 4f¹⁴ 5d¹⁰ 6s¹

11. What are the common oxidation states of Gold?

    • +3, +1

12. What is the appearance of Gold?

    • Yellow metallic

13. Is Gold reactive with air?

    • No, it is resistant to corrosion and tarnishing.

14. Name a compound of Gold.

    • Gold chloride (AuCl₃)

15. What is a common use of Gold in jewelry?

    • Valued for its aesthetic appeal and resistance to tarnish.

16. How is Gold used in electronics?

    • Used for connectors, switches, and relay contacts.

17. What role does Gold play in finance?

    • Employed as a standard for currency and as an investment.

18. How is Gold used in dentistry?

    • Used in dental alloys for crowns and bridges.

19. What application does Gold have in medicine?

    • Used in treatments for rheumatoid arthritis and diagnostic procedures.

20. How is Gold used in aerospace?

    • Used in reflective coatings for satellites and spacecraft.

21. Name a mineral that contains Gold.

    • Often found in association with quartz and sulfide minerals.

22. How is Gold extracted from ores?

    • Through mining methods like placer mining, panning, sluicing, and dredging.

23. What is the most stable isotope of Gold?

    • Gold-197

24. Name a radioactive isotope of Gold used in research.

    • Gold-198

25. What safety hazard is associated with Gold compounds?

    • Some compounds can be toxic if ingested or inhaled.

26. Where does the name Gold come from?

    • From the Old English word “geolu,” meaning yellow.

27. What is the crystal structure of Gold?

    • Face-centered cubic (fcc)

28. Is Gold paramagnetic or diamagnetic?

    • Diamagnetic

29. What is the thermal conductivity of Gold?

    • About 318 W/m·K

30. What is the electrical resistivity of Gold at room temperature?

    • About 22.14 nΩ·m

31. What is the primary oxidation state of Gold?

    • +3

32. Is Gold found as a free element in nature?

    • Yes, often in rocks, veins, and alluvial deposits.

33. What is the common name of Gold cyanide?

    • Au(CN)₂⁻

34. What is a major application of Gold oxide (Au₂O₃)?

    • Used in chemical research and industrial applications.

35. How does Gold benefit electronics?

    • Provides excellent conductivity and resistance to corrosion.

36. What is the boiling point of Gold in Kelvin?

    • 3243 K

37. What group does Gold belong to in the periodic table?

    • Transition metals

38. What is the natural abundance of Gold-197?

    • 100%

39. Can Gold be used in high-temperature applications?

    • Yes, due to its high melting point and stability.

40. What is the key property that makes Gold valuable in jewelry?

    • Its aesthetic appeal and resistance to tarnish.