What is the relationship between the molar mass of Ne, Ar, Kr, and Xe and the melting points of their solids?
The general rule is that melting point increases as the molar mass increases.
Here is a table that list the melting points (other properties, also) for all of the noble gases.
http://en.wikipedia.org/wiki/Noble_gas#Physical_and_atomic_properties
Thanks! But, does this rule apply to any molecular compounds. I noticed that for H2O, H2S, H2Se H2Te, the rule applies to H2S to H2Te but is different for H2O. Why is that??
Because of hydrogen bonding. If you will note, the boiling point decreases from H2Te to H2Se to H2S but the electronegativity of O is large enough that H bonding takes a much larger effect. As a result the boiling point for H2O is much higher than we would expect it to be.(We might expect it to be a gas.) Does this happen with other groups? You bet it does and for the same reason. N, O, and F are the main ones that we have H bonding. Look at the boiling points of SbH3, AsH3, PH3, and NH3. The latter is way off target. Same thing with HI, HBr, HCl, HF.
To understand the relationship between the molar mass of noble gases (Ne, Ar, Kr, and Xe) and the melting points of their solids, we need to consider the concept of intermolecular forces.
The melting point of a substance is influenced by the strength of the forces holding its particles together. In the case of noble gases, these forces are called London dispersion forces or van der Waals forces. London dispersion forces arise due to temporary fluctuations in the electron cloud around an atom or molecule, which induce similar fluctuations in neighboring atoms or molecules. These induced dipoles attract each other and contribute to intermolecular forces.
The strength of London dispersion forces depends on various factors, including the molar mass or size of the atoms or molecules. Generally, larger atoms or molecules tend to have stronger London dispersion forces because they have more electrons. More electrons result in larger temporary fluctuations in the electron cloud, increasing the strength of the induced dipoles and overall intermolecular forces.
In the case of Ne, Ar, Kr, and Xe, they are all noble gases and consist of individual atoms. As we move down the periodic table from Ne to Xe, the molar mass of the noble gases increases. Therefore, Xe has the largest molar mass among the four gases.
Based on the relationship between molar mass and London dispersion forces, we can conclude that Xe has the highest melting point among Ne, Ar, Kr, and Xe. This is because the larger molar mass of Xe results in stronger London dispersion forces, which requires more energy to break the intermolecular attractions and convert the solid into a liquid.
However, it is important to note that while molar mass is a significant factor influencing melting points in these noble gases, it is not the only factor. Other factors, such as the atomic radius and electronic structure, can also affect the strength of intermolecular forces and ultimately the melting point.