Metals, Minerals, Ores : Properties, Uses Part-1

Copper (Cu): Approximately $8.96\text{g/cm³}$

Uranium (U): Approximately $19.05-19.1\text{g/cm³}$

Aluminium (Al): Approximately $2.70\text{g/cm³}$

Silver (Ag): Approximately $10.5\text{g/cm³}$

Uranium is the heaviest naturally occurring element with an atomic no. of 92. It is a pure form of silver-coloured heavy metal. Its most common isotope Uranium-238 has a nucleus containing 92 protons and 146 neutrons. It has a density of 19.05 g/cm³.

The approximate densities of the metals listed:

Gold (Au): $19.32\text{g/cm³}$

Silver (Ag): 10.49g/cm³

Mercury (Hg): 13.534g/cm³ (liquid at room temperature)

Platinum (Pt): 21.45g/cm³

Among the given options, platinum is the heaviest metal with a density of 21.09 g/cm³.

From the above list, it is clear that Endohedral Fullerene is the costliest material of the world discovered recently. However, the question asked about the costliest metal, and it is not the correct answer. Californium-252 is the costliest metal but it was not discovered recently. So, the question seems to be incorrect.

The chemical composition of pearl is 86%  to 92% Calcium Carbonate (Aragonite), 10-14% Conchiolin and 2-4% water (CaCO₃, H₂O).

The main constituents of a pearl are:

Aragonite: This is a specific crystalline form of calcium carbonate (CaCO₃​). Pearls are primarily composed of microscopic crystals of aragonite, which give them their iridescent luster.

Conchiolin: This is an organic protein that acts as a natural "glue" or matrix, binding the layers of aragonite crystals together. It provides the pearl with its structure and resilience.

These two components are layered repeatedly by the mollusk to form the pearl.

The chemical composition of pearl is 86%  to 92% Calcium Carbonate (Aragonite), 10-14% Conchiolin and 2-4% water (CaCO₃, H₂O).

Rubies and Sapphires are both gem varieties of the mineral Corundum. Chemically, corundum is Aluminium Oxide (Al₂​O₃). which owe their characteristic colours to trace impurities.

The difference in color between rubies (red) and sapphires (typically blue, but can be almost any other color) comes from the presence of trace elements (impurities) within the aluminium oxide crystal structure:

Rubies get their red color from trace amounts of chromium (Cr).

Blue Sapphires get their blue color from trace amounts of iron (Fe) and titanium (Ti). Other colors of sapphire are due to other trace elements.

Therefore, chemically, they are both Aluminium Oxide.

Sodium is kept in kerosene to prevent it from coming in contact with oxygen present in the air. If this happens, it will react with the oxygen, and sodium oxide is formed. This is a strongly exothermic reaction, and a lot of heat is generated. Thus, Sodium is kept under kerosene.