Sodium is a soft metal. Most of the elements known to us are metals. They are monoatomic. Most of them are hard, malleable, ductile and sonorous solids, apart from a few exceptions. Sodium and potassium are known as soft metals as they can be cut by a knife. Mercury is the only metal that is present in the liquid state.

Mercury is a liquid metal. Most of the elements known to us are metals. They are monoatomic. Most of them are hard, malleable, ductile and sonorous solids, apart from a few exceptions.

Helium is an inert gas. Inert or noble gases are monoatomic gaseous elements which do not react chemically with other elements or compounds, so they are known as noble or inert gases. They are found in air, in traces. They are only six in numbers- helium, neon, argon, krypton, xenon and radon.