Question

All noble gases molecules are _______ (monoatomic / diatomic).

Answer 1

Noble gases: These are the non-reactive gases also known as inert gases.

• The group 18 elements in the periodic table are noble gases.

1. Helium $\left(\mathrm{He}\right)$
2. Neon $\left(\mathrm{Ne}\right)$
3. Argon $\left(\mathrm{Ar}\right)$
4. Krypton $\left(\mathrm{Kr}\right)$
5. Xenon $\left(\mathrm{Xe}\right)$
6. Radon $\left(\mathrm{Rn}\right)$

• All the noble gases have completely filled the valence shell.
• The general outer electronic configuration of noble gases (group 18) is ${\mathrm{ns}}^2{\mathrm{np}}^6$ (except Helium - $1{\mathrm{s}}^2$).
• Since noble gases are unreactive, they exist in the monoatomic form in nature. Monoatomic means that an element exists as a single atom, not in its molecular form.
• Diatomic means that an element exists as a molecule consisting of two atoms. Example- Oxygen gas $\left({\mathrm{O}}_2\right)$

Hence, the correct answer is monoatomic.