The noble gases

Group 0 (IUPAC group 18) is a vertical column on the far right of the periodic table. The elements in group 0 are non-metals called the noble gases. They exist as single atoms.

Periodic table with the Group 0 Noble Gases coloured in red.Group 0 (IUPAC group 18) is on the far right-hand side of the periodic table

The noble gases show trends in their physical properties.

Trends in physical properties

Boiling point

The noble gases all have low boiling points:

  • helium, at the top of group 0, has the lowest boiling point of any element
  • boiling point increases going down the group
Bar chart of the boiling points of elements in Group 0The boiling points of group 0 elements

This is because, going down group 0:

Density

The density of a substance is its mass per unit volume. For example, a small piece of a substance with a high mass has a high density.

The particles in gases are widely spaced, so the noble gases have low densities:

  • helium, at the top of group 0, has the lowest density in the group
  • density increases going down the group
Bar chart of the density of six Group 0 elements.The densities of group 0 elements
Question

Oganesson, Og, was discovered in 2002. It is placed below radon in group 0. Assuming that it is a gas at room temperature, predict its density and explain your answer.

About 16 g/cm3 because density increases going down group 0, and the difference increases from one element to the next.

Chemical properties

The noble gases are all inert - they are extremely unreactive. Unlike elements in other groups, their atoms have complete outer shells. This means that atoms of the noble gases have no tendency to lose, gain, or share electrons. When other elements react, their atoms complete their outer shells by losing, gaining, or sharing electrons.

ElementElectron arrangement
Helium, He2
Neon, Ne2.8
Argon, Ar2.8.8

The periodic table, containing all the known elements, arranged in groups and periods