Question

It is possible to change the temperature and pressure of a vessel containing argon gas so that the gas solidifies. (a) What intermolecular forces exist between argon atoms? (b) Is the solid argon a "covalent network solid"? Why or why not?

Short answer

(a) The intermolecular forces between argon atoms are van der Waals forces, also known as London dispersion forces or weak inter-atomic forces, arising from temporary fluctuations in electron density. (b) Solid argon is not a covalent network solid because it does not consist of a continuous network of covalent bonds. Instead, it is held together by weak van der Waals forces, resulting in a relatively low melting temperature compared to covalent network solids.

Step-by-step solution

(a) Intermolecular Forces in Argon

Argon, being a noble gas (having a filled valence electron shell) is chemically inert and does not form molecules. Therefore, the intermolecular forces in argon gas are van der Waals forces, also known as London dispersion forces or weak inter-atomic forces. This type of force arises from temporary fluctuations in electron density around the argon atoms, which create instant dipoles that induce dipoles on neighboring atoms.

(b) Determine if Solid Argon is a Covalent Network Solid

A covalent network solid is a type of covalent crystal in which the atoms are joined together by a network of covalent bonds. These types of solids are generally very hard, brittle, and have high melting temperatures due to the strength of the covalent bonds in the network. Examples of covalent network solids include diamond, silica, and graphite. Solid argon, on the other hand, is composed of argon atoms held together by the weak van der Waals forces mentioned earlier. These forces are significantly weaker than the covalent bonds present in covalent network solids, resulting in solid argon having a relatively low melting temperature compared to covalent network solids. As a result, solid argon is not considered a covalent network solid because it does not consist of a continuous network of covalent bonds but instead is held together by weak van der Waals forces.