Explanation of the religion and use of coin metal
Question: What are Coinage Metals?
Answer: Copper (Cu), Silver (Ag), and Gold (Au), which belong to Group IB (Group 11) of the periodic table, are collectively called Coinage Metals. They are named so because these metals have been widely used since ancient times to mint coins and currency.
The electronic configuration of the valence shell of these elements is (n-1)d10ns1. Due to the presence of a single electron (ns1) in their outermost energy level, they are placed in Group I. Furthermore, because their differentiating (last) electron enters the d-orbital, they are classified under the ‘B’ subgroup, resulting in their placement in Group-IB.
Chemical Properties of Coinage Metals:
- i. Variable Oxidation States: They exhibit variable oxidation states due to the participation of d-electrons in bonding.
- ii. Stability in Air: They remain stable and unreactive in dry air at room temperature.
- iii. Action with Water: They do not react with water or steam under normal temperatures.
- iv. Action with Alkalis: They do not react with alkalis under ordinary conditions.
- v. Action with Acids: Copper (Cu) and Silver (Ag) react with oxidizing acids to form their respective salts. Gold (Au) is highly unreactive but dissolves in Aqua Regia (a mixture of concentrated HCl and HNO3 in a 3:1 ratio).
3. Sources of Coinage Metals:
The primary sources of coinage metals are their respective ores:
A. Major Ores of Copper (Cu):
- Copper Pyrites (Chalcopyrite) – CuFeS2
- Malachite – CuCO3·Cu(OH)2
- Cuprite (Ruby Copper) – Cu2O
- Chalcocite (Copper Glance) – Cu2S
- Azurite – 2CuCO3·Cu(OH)2
B. Major Ores of Silver (Ag):
- Argentite (Silver Glance) – Ag2S
- Pyrargyrite (Ruby Silver) – 3Ag2S·Sb2S3
- Horn Silver (Cerargyrite) – AgCl
- Proustite (Light Ruby Silver) – Ag3AsS3
C. Major Ores of Gold (Au):
In nature, gold mostly occurs in its native (free) state associated with various rocks. It is frequently found in auriferous rocks mixed with sulfide ores like iron pyrites. Additionally, it occurs in combined forms such as:
- Calaverite – AuTe2
- Sylvanite – (Ag, Au)Te2
Uses of Coinage Metals
A. Uses of Copper (Cu):
- i. Widely used in making electrical wires and telephone cables due to its high electrical conductivity.
- ii. Extensively used in electroplating processes.
- iii. Used in minting coins and currency.
- iv. Used in manufacturing household utensils.
- v. Used to produce crucial alloys such as Brass (Cu: 60–80% and Zn: 20–40%) and Bronze (Cu: 75–90% and Sn: 10–25%).
B. Uses of Silver (Ag):
- i. Primarily used for making premium coins and medals.
- ii. Extensively used in crafting jewelry, ornaments, and fine silverware.
- iii. Widely used in traditional photography (in the form of Silver Halides).
- iv. Used in the silvering of mirrors for high reflectivity.
- v. Used in dental amalgams (alloys) for tooth fillings.
C. Uses of Gold (Au):
- i. Extensively used in making jewelry, ornaments, and as a standard store of value.
- ii. Used in minting commemorative coins and bullion.
- iii. Used in gold electroplating and microelectronics for its excellent corrosion resistance.
- iv. Used in preparing Purple of Cassius (a colloidal gold stain), which is heavily utilized as a pigment in manufacturing ruby glass and fine porcelain.
