describe the predominant forces that exist between molecules of the noble gases. Arrange the noble gases in a predicted order of increasing boiling point (lowest first) and explain the reason for the order
Intermolecular forces, primarily dispersion forces and induced dipole-induced dipole forces increase as the atomic mass and size increases.
The predominant forces that exist between molecules of noble gases are known as London dispersion forces, also called van der Waals forces. These forces result from temporary fluctuations in electron distribution, causing an instantaneous dipole in one atom which then induces a dipole in a neighboring atom. This causes a weak attraction between the two atoms, resulting in a London dispersion force.
London dispersion forces are the only intermolecular force acting on noble gas molecules because they consist of single atoms rather than molecules with permanent dipoles. Noble gases are considered to be chemically inert due to their full valence electron shells, which makes them stable and resistant to forming chemical bonds.
When arranging the noble gases in a predicted order of increasing boiling point, we need to consider the atomic size and the number of electrons. As we move down the group of noble gases in the periodic table, both the atomic size and number of electrons increase.
The increase in atomic size leads to larger electron clouds, resulting in stronger London dispersion forces. At the same time, the increase in the number of electrons also contributes to stronger London dispersion forces due to a greater chance of temporary fluctuations in electron distribution.
So, the predicted order of increasing boiling point (lowest first) among noble gases is as follows:
1. Helium (He)
2. Neon (Ne)
3. Argon (Ar)
4. Krypton (Kr)
5. Xenon (Xe)
6. Radon (Rn)
Helium has the lowest boiling point because it is the smallest noble gas with the fewest number of electrons, resulting in weaker London dispersion forces. As we move down the group, the atomic size and the number of electrons increase, leading to stronger London dispersion forces and higher boiling points.
It's important to note that the boiling points of noble gases are quite low compared to other substances due to the relatively weak London dispersion forces involved.