Chemistry of Metals and Alloys

Bell metal is an alloy and consists of Cu = 80%, Sn = 20%. Wood metal consists of Bi = 50%, Pb = 25%, Sn = 12.5% & Cd = 12.5% and is used in the making of automatic sprinklers as it melts in hot water (m.p.= 68 ^oC). Duralumin is used in the manufacturing of aeroplane parts and consists of Al = 95.5%, Cu = 4%, Mg = 0.5% and Mn = 0.5%.

Silicon is a semiconductor material and is used in chip manufacturing.

Boron carbide is an extremely hard boron-carbon ceramic material used in tank armour, bulletproof vests, and numerous industrial applications. With a Mohs hardness of above 9, it is one of the hardest materials known, behind cubic boron nitride and diamond.

Nichrome is a non-magnetic alloy of nickel, chromium, and often iron, usually used as a resistance wire . Due to its relatively high electrical resistivity and resistance to oxidation at high temperatures, it is widely used in electric heating elements, such as in hair dryers, electric ovens, soldering iron, toasters, and even electronic cigarettes.

Elektron is a magnesium alloy. It is unusually light and has a specific gravity of about 1.8 compared with  2.8 of aluminium alloy.The alloy variants are used in auto racing and aerospace engineering applications due to magnesium's relatively low density.

Electrum is a naturally occurring alloy of gold and silver, with trace amounts of copper and other metals. Electrum was used as early as the third millennium BC in Old Kingdom of Egypt, sometimes as an exterior coating to the pyramidions atop ancient Egyptian pyramids and obelisks.

Mischmetal is an alloy of rare earth elements in various naturally-occurring proportions. A typical composition includes approximately 50% cerium and 25% lanthanum, with small amounts of neodymium and praseodymium. Its most common use is in the flint ignition device of many lighters and torches.

Megallium is an alloy of 60% cobalt, 20% chromium, 5% molybdenum, and traces of other substances. It is used in dentistry because of its light weight, resistance to corrosion and hypo-allergenic (nickel free) properties.

Stainless steel requires at least 10.5% chromium, which forms a protective oxide layer on the surface that prevents rust and corrosion. This chromium oxide layer is self-repairing when scratched in the presence of oxygen.

Numismatic evidence confirms that Satavahana coins were minted in copper, lead, potin (a copper alloy), and silver. Gold was not a standard metal for their coinage, eliminating options A and D. Option C matches the historical record.

German silver, also known as nickel silver, is an alloy composed of copper, nickel, and zinc - it contains NO actual silver despite its name. The name comes from its silver-like appearance. Silver (option C) is indeed not present in German silver, which is why this answer is correct.

Magnesium is commercially extracted from seawater through the Dow process. Seawater contains magnesium salts (mainly magnesium chloride) which can be precipitated and processed to obtain magnesium metal. The other metals listed are not obtained from seawater.

Cadmium fluoride is a mostly water-insoluble source of cadmium used in oxygen-sensitive applications, such as the production of metallic alloys. In extremely low concentrations (ppm), this and other fluoride compounds are used in limited medical treatment protocols.

Steel is fundamentally an alloy of iron and carbon, with carbon content typically between 0.02% to 2.1% by weight. Option A is correct as carbon is the primary alloying element that distinguishes steel from pure iron. While steel can contain other elements like manganese, chromium, or nickel in varying amounts depending on the type, the basic definition is iron-carbon alloy.

Copper was the first metal used by humans because it occurs naturally in its pure form and is relatively soft, making it easy to work with. Ancient civilizations used copper for tools, weapons, and ornaments long before discovering how to smelt iron or create alloys like bronze.