The noble gases have low boiling points.
But their boiling points do increase as you move down the periodic table. This is because the relative atomic mass increases lower down the periodic table.
why?
The boiling point of an element is influenced by the strength of the intermolecular forces between its atoms or molecules. In the case of noble gases, the only intermolecular force present is the weak van der Waals force, which arises due to the fluctuations in electron density around the atoms. The strength of this force increases with increasing atomic or molecular size, because larger atoms/molecules have more electrons and therefore a larger electron cloud that can be distorted, leading to greater attractions between them. Therefore, as we move down the group of noble gases, the atomic size and relative atomic mass increase, resulting in stronger van der Waals forces and higher boiling points.
The boiling points of noble gases increase as you move down the periodic table because the relative atomic mass increases lower down the periodic table. This is due to the increase in the number of protons and neutrons in the nucleus as you move down the group.
The boiling point is a measure of the strength of intermolecular forces between particles in a substance. In noble gases, these intermolecular forces are van der Waals forces, specifically London dispersion forces. These forces result from temporary imbalances in electron distribution, causing temporary dipoles.
The strength of London dispersion forces depends on the size or atomic radius of the atoms or molecules involved. As the atomic radius increases down the group, there is a larger electron cloud, which means a greater potential for temporary dipoles to occur and stronger attractive forces between the atoms or molecules.
Therefore, the increase in boiling points of noble gases as you move down the periodic table is primarily due to the increase in atomic radius and the corresponding increase in London dispersion forces.