Question

Why noble gas elements are called rare elements?

Answer 1

Part 1: Noble gas elements:

• Noble gases are the elements that have completely filled valence shells i.e. their octets are completely filled.
• Due to completely filled octet, they are highly stable and hence do not tend to form chemical bonds.
• Noble gases are Helium $\mathbf{\left(}\mathbf{He}\mathbf{\right)}$, Neon $\mathbf{\left(}\mathbf{Ne}\mathbf{\right)}$, Argon $\mathbf{\left(}\mathbf{Ar}\mathbf{\right)}$, Krypton $\mathbf{\left(}\mathbf{Kr}\mathbf{\right)}$, Xenon $\mathbf{\left(}\mathbf{Xe}\mathbf{\right)}$ and Radon $\mathbf{\left(}\mathbf{Rn}\mathbf{\right)}$.
• In the atmosphere, noble gases are found in trace amount therefore they are called rare elements.

Part 2: Abundance of noble gases in earth's atmosphere:

• Helium $\mathbf{\left(}\mathbf{He}\mathbf{\right)}$ - $0.00052\%$
• Neon $\mathbf{\left(}\mathbf{Ne}\mathbf{\right)}$ - $0.0018\%$
• Argon $\mathbf{\left(}\mathbf{Ar}\mathbf{\right)}$ - $0.934\%$
• Krypton $\mathbf{\left(}\mathbf{Kr}\mathbf{\right)}$ - $0.0001\%$
• Xenon $\mathbf{\left(}\mathbf{Xe}\mathbf{\right)}$ - $0.000009\%$
• Radon $\mathbf{\left(}\mathbf{Rn}\mathbf{\right)}$ is a radioactive noble gas and is not present in the atmosphere.

Thus, noble gas elements are called rare elements.