Chemistry of Metals and Alloys

Metallic character refers to the tendency to lose electrons. Li, Na, K and Rb are the members of group 1. As we move down the group from Li to Rb, the atomic size increases because the number of shells increases. Due to this increased atomic size, the effective nuclear charge experienced by electrons present in the outermost shell decreases. As a result, it becomes easier for an element to lose its electron, i.e. on moving down the group, metallic character increases. Therefore, Li is the least metallic, whereas Rb is the most metallic from all the given elements.

Tungsten (W) is used for electric bulb filaments because it has the highest melting point of all metals at approximately 3422°C (6192°F), allowing it to remain solid and emit light at the high temperatures (~2500°C) needed for bright illumination. It also has very low vapor pressure at high temperatures, meaning it doesn't evaporate quickly. Nichrome (nickel-chromium alloy) is used for heating elements, not light bulb filaments. Iron would melt quickly at bulb operating temperatures.

Silver has the highest electrical conductivity of all metals, approximately 6.30×10^7 S/m at room temperature. This means it allows electric current to pass through it with the least resistance. Gold and copper are also excellent conductors, but silver outperforms all metals in conductivity.

 Antimony is used in fireworks.

Sodium has low melting and boiling points.

Car batteries are lead-acid batteries, using lead dioxide as the positive plate and sponge lead as the negative plate, with sulfuric acid as the electrolyte. The lead-acid chemistry provides the high current needed for engine starting and the rechargeability required for automotive use. This technology has been the standard for over 100 years.

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Nichrome (nickel-chromium alloy) is the standard material for heating elements because it has high electrical resistance, can withstand temperatures over 1000°C without oxidizing, and maintains structural integrity when heated repeatedly. Tungsten has a very high melting point but is used in incandescent bulb filaments, not heating elements. Pure iron would oxidize and rust quickly at high temperatures. Chromium alone is not used for heating elements - it's the chromium in nichrome that provides corrosion resistance.

Metals are good conductors of heat and electricity.

Mercury is in a liquid state at room temperature. 

Sodium is a soft metal, and it can be easily bent with a knife.

Iron forms a part of haemoglobin of blood.

Copper was the first metal used by humans, dating back to around 8000 BCE during the Chalcolithic period (Copper Age). Its natural occurrence in native form, malleability, and lower melting point compared to other metals made it ideal for early tool-making and ornamental purposes before bronze and iron discovery.

The Harappans used gold, copper, silver, and bronze extensively. However, they did not use iron, as iron technology came to India after the decline of the Indus Valley Civilization with the advent of the later Vedic period and the Iron Age around 1200 BCE. The Harappan civilization was primarily a Bronze Age civilization.