Chemistry of Metals and Alloys

Zinc, also referred to in non-scientific contexts as spelter, is a bluish-white, lustrous, diamagnetic metal though most common commercial grades of the metal have a dull finish. It is somewhat less dense than iron and has a hexagonal crystal structure.

Iron is a metal in the first transition series. It is the most common element in the whole planet Earth, forming much of the earth's outer and inner core, and it is the fourth most common element in the earth's crust. It is ferromagnetic around room temperature.

Tungsten is used as the filament in incandescent bulbs because it has an extremely high melting point (3,422°C) and resists vaporization at the high temperatures needed to produce visible light. Other metals like iron, nickel, or copper would melt or evaporate too quickly at these operating temperatures.

Iron was the most important metal during the Gupta Age, essential for weapons, agricultural tools, and construction. The period saw significant advances in iron metallurgy, including the famous iron pillar at Mehrauli (Delhi) that has resisted corrosion for over 1,600 years. While gold and silver were used for coinage and ornaments, iron's practical applications made it most crucial.

The Harappan civilization extensively used copper, bronze, gold, and silver based on archaeological finds. However, they did not use iron - the Iron Age in India began much later around 1000 BCE, while Harappan civilization flourished around 2600-1900 BCE during the Chalcolithic (Copper-Stone) period. Tin was used primarily in bronze alloy, not separately.

Ag is the chemical symbol for silver, derived from the Latin word 'argentum'. Gold is Au, platinum is Pt, and lead is Pb.

Ruby (red due to chromium impurities) and sapphire (blue due to iron/titanium impurities) are both gem varieties of the mineral corundum, which is crystalline aluminum oxide (Al2O3). They are among the hardest gemstones after diamond.

Computer disc does not contain mercury.

Both bismuth and antimony are diamagnetic materials, meaning they are weakly repelled by a magnetic field and do not retain magnetic properties when the external field is removed. Diamagnetic substances have all their electrons paired and no permanent magnetic moment. This property contrasts with paramagnetic and ferromagnetic materials.

Chromium is the key component in heating element alloys like nichrome (nickel-chromium). Pure chromium isn't used alone, but among these options, it's the only element relevant to resistance heating alloys.

Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive. It is hard and brittle.

Heating elements are made of chromium (in the form of nichrome alloy with nickel). Chromium has high electrical resistance and high melting point, making it ideal for converting electrical energy to heat without degrading. Iron would rust, silver is too expensive and has low resistance, and zinc has too low a melting point.

Bronze is primarily an alloy of copper (about 88%) and tin (about 12%). This combination gives bronze its characteristic properties like corrosion resistance and low friction. Copper-zinc makes brass, copper-nickel makes cupronickel, and copper-chromium isn't a standard alloy.

Gold is one of the few metals that occurs naturally in its pure (native) metallic state. This is because gold is relatively unreactive and doesn't easily combine with other elements. Copper, iron, and zinc are usually found as ores (compounds) and require smelting to extract the pure metal.