Group 0: The Noble Gases

Boiling and Melting Points

• As you move down the group, the boiling and melting points increase. This occurs because the atoms become larger and have a higher relative atomic mass.
• Larger atoms experience stronger intermolecular forces (specifically Van der Waals forces). More energy is required to overcome these forces to change the state from liquid to gas.

Density

• The density of noble gases increases as you move down the group. This is due to the increase in atomic mass as you descend from Helium to Radon.
• Despite this increase, all Group 0 elements remain significantly less dense than air or other common substances at room temperature.

It is essential to distinguish noble gases from reactive non-metals like Halogens (Group 7).

• Predicting Values: Exams often provide data for two elements and ask you to estimate a third. Always follow the trend: if moving down the group, the boiling point and density must be higher than the element above it.

• The Helium Trap: Never state that all noble gases have eight electrons in their outer shell. Always specify that Helium has two, while the rest have eight.

• Explaining Inertness: When asked why they are unreactive, focus your answer on the stable electronic configuration provided by the full outer shell. Avoid saying they 'don't want' to react; use scientific terms like 'energetically stable'.

• Intermolecular Forces: When explaining the boiling point trend, explicitly link the increase in atomic size to the increase in intermolecular forces.