Question

The metal which is lighter than water is:
A. Lithium
B. Gold
C. Silver
D. Iron

Answer 1

Hint: In metallurgy, for instance, a hefty metal might be characterized based on thickness, though in material science the distinctive rule may be nuclear number, while a scientific expert would almost certainly be more worried about substance conduct. More explicit definitions have been distributed, yet none of these have been generally acknowledged.

Complete step by step solution:
Substantial metals are commonly characterized as metals with generally high densities, nuclear loads, or nuclear numbers. The rules utilized, and whether metalloids are incorporated, change contingent upon the creator and context. In metallurgy, for instance, a hefty metal might be characterized based on thickness, though in material science the distinctive rule may be nuclear number, while a scientific expert would almost certainly be more worried about substance conduct. More explicit definitions have been distributed, yet none of these have been generally acknowledged.
Density is mass divided by volume \[\left( {\rho = m/v} \right),\]and water was used as the basis for establishing the metric unit of mass, which means a cubic centimetre (\[1c{m^3}\]) of water weighs one gram (\[1g\]). So, \[1g/1c{m^3}{\rm{ }} = {\rm{ }}1{\rm{ }}g/c{m^3}\], giving water it's easy-to-remember density.
Whereas we know density of Lithium is $0.534g/c{m^3}$
The density of gold is $19.3\,g/c{m^3}$
The density of gold is $10.49\,g/c{m^3}$
The density of iron is $7.874\,g/c{m^3}$
The lightest or least thick metal that is an unadulterated component is lithium, which has a thickness of $0.534g/c{m^3}$. This makes lithium almost half as thick as water, so if lithium was not all that responsive, a lump of the metal would glide on water.

Hence option (A) is the correct answer.

Note:
The density of any element decides either metal is lighter or not. On observation, we get to know that Lithium is the only one among the four options whose molar mass is less than molar mass of water. Volume of one mole of either of the substances at STP would be the same i.e 22.4 L. This is another method of finding the correct answer.