Chemistry of Metals and Alloys

Mercury is the only metal in liquid form.

Iron is an element.

Lead dioxide (PbO2) is used as the active material in the positive plates of lead storage batteries (lead-acid batteries). It undergoes reduction during discharge, converting to lead sulfate.

The largest consumer of tellurium is metallurgy, where it is used in iron, copper and lead alloys. When added to stainless steel and copper it makes these metals more machinable.

Stainless steel contains at least 10.5% chromium, which forms a protective oxide layer on the surface. This layer prevents corrosion and gives stainless steel its rust-resistant properties. Nickel and molybdenum are often added too.

The Indus Valley Civilization (c. 3300-1300 BCE) flourished during the Bronze Age and was proficient in copper and bronze metallurgy. However, iron working was not known to the Harappan people - iron technology came to the Indian subcontinent much later, around 1000 BCE, marking the beginning of the Iron Age in India.

There are many different bronze alloys, but modern bronze is 88% copper and 12% tin.

All the given metal and alloy pairs are correct. The given alloys are made up by combining these metals with some other metals.

Sodium is a soft metal. It can be easily cut into pieces using a knife.

The reactivity series is a series of metals, in order of reactivity from the highest to the lowest. In this series, zinc lies in between magnesium and lead.

Mercury is a bad conductor of heat.

Both Co₃O₄ and MgAl₂O₄ are normal spinels.

'Useful' begins with a consonant sound /j/ (as in 'you'), not a vowel sound, so the correct article is 'a.' Articles are determined by the spoken sound that follows, not the written letter. Even though 'useful' starts with 'u,' it takes 'a' because the /j/ sound is consonantal.

Gallium has an unusually low melting point of 29.76°C (approximately 85.6°F), which means it becomes liquid at normal room temperature (typically 20-25°C). While mercury and bromine are also liquids at room temperature, mercury is the only other metal that's liquid under standard conditions, and it's not listed among the options.

Gold is a noble metal that doesn't readily oxidize or react with other elements, allowing it to exist in pure metallic form (native state) in nature. Unlike silver, copper, or bronze (which is an alloy), gold is found in nuggets or veins in its elemental form without chemical processing. This property has made gold valuable throughout human history.