Copper was the first metal to be extensively used by humans, marking the beginning of the Copper Age (Chalcolithic period). It was relatively easy to extract from its ores and could be hammered into tools and ornaments before the development of smelting and alloying techniques like bronze or iron working.
92
Which of the following metals is typically found in its native (uncombined) state in nature?
Gold is a noble metal with a very low reactivity, meaning it does not easily oxidize or react with other elements in the environment. Consequently, it is frequently found in its elemental, metallic form in nature, unlike reactive metals like aluminium or zinc, which are found as ores.
93
Which category of elements is characterized by the ability to exhibit variable valency?
Transition elements, or d-block elements, possess partially filled d-orbitals. Because the energy difference between the (n-1)d and ns orbitals is small, these elements can lose electrons from both subshells, allowing them to exhibit multiple oxidation states or variable valency.
94
Malachite is a naturally occurring ore of which metal?
Malachite is a green copper carbonate hydroxide mineral with the chemical formula Cu2CO3(OH)2. It has been used as a copper ore for thousands of years and is also prized as a gemstone due to its distinct green banding and color, which results from the presence of copper ions.
95
Vitamin B12 deficiency leads to pernicious anemia. Since animals cannot synthesize it, it must be obtained through diet. Which metal ion is the central complexing agent in Vitamin B12?
Vitamin B12, also known as cobalamin, is a complex organometallic compound. Its structure features a central cobalt ion (Co3+) coordinated within a corrin ring system. This cobalt center is essential for the vitamin's biological activity in DNA synthesis and neurological function.
96
Which of the following substances does not contain silver?
Despite its name, German silver is an alloy consisting primarily of copper, nickel, and zinc. It contains no silver at all. Horn silver is silver chloride, ruby silver is a silver-antimony sulfide mineral, and lunar caustic is silver nitrate.
97
Why is tin preferred over zinc for coating food storage utensils?
Zinc is more chemically reactive than tin. If zinc were used to coat food utensils, it would react more readily with acidic food components, potentially leaching harmful zinc ions into the food. Tin is less reactive and provides a safer, more stable protective barrier for food-grade containers.
98
Which of the following elements is historically referred to as 'Aurum'?
The term 'Aurum' is the Latin word for gold, from which the chemical symbol 'Au' is derived. It is a noble metal known for its distinct yellow luster and high resistance to corrosion.
99
Some substances are good conductor of electricity in both the solid and liquid states. These substances are generally______________?
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100
Which element exhibits the highest oxidation state?
