Physical Properties-

• Noble gases 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 because:

  • The atoms become larger
  • The intermolecular forces between the atoms become stronger
  • More energy is needed to overcome these forces
• Density is the mass per unit volume of a substance
• A small piece of a substance with a high mass has a high density
• The particles in gases are widely spaced, so 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