Utilice una obra de consulta como el CRC Handbook of...

Utilice una obra de consulta como el CRC Handbook of Chemistry and Physics para comparar los puntos de fusión y de ebullición de los pares de sustancias inorgánicas siguientes: (a) $\mathrm{W}_{\mathrm{y}} \mathrm{WF}_6$ (b) $\mathrm{SO}_2$ y $\mathrm{SF}_4$; (c) $\mathrm{SiO}_2$ y SiCl 4 . $\mathrm{Ex}$ plique las diferencias importantes observadas en términos de probables estructuras y enlaces.

Key Concepts

Chemical Bonding and Structure

This concept involves understanding the nature of the bonds between atoms in a compound. In inorganic compounds, bonds can range from strong network covalent bonds that extend across a whole crystal lattice to weaker intermolecular bonds present in discrete molecules. The type of bonding is fundamental in determining physical properties such as melting and boiling points, as compounds with extensive covalent networks typically require much more energy to break apart compared to those with only van der Waals forces holding molecules together.

Intermolecular Forces

Intermolecular forces are the forces of attraction between discrete molecules. These include dipole-dipole interactions, London dispersion forces, and hydrogen bonds. The strength and type of these interactions have a direct impact on melting and boiling points; stronger intermolecular forces generally result in higher phase transition temperatures. In compounds where molecular polarity is present, these forces can be significantly stronger, influencing the substance's physical behavior.

Molecular Geometry and Polarity

The three-dimensional arrangement of atoms within a molecule, or molecular geometry, plays a crucial role in determining the molecule’s polarity. Polarity leads to dipole moments that affect the type and strength of intermolecular interactions. Different geometries can result in varying degrees of molecular asymmetry, which in turn influences melting and boiling points by affecting how molecules pack in the solid state and interact in the liquid or gas phase.

Network Covalent Structures vs. Discrete Molecular Structures

Some inorganic substances form continuous three-dimensional networks through covalent bonding, creating highly stable and rigid structures that require large amounts of energy to thermally disrupt, thus showing high melting points and often no conventional boiling point. In contrast, substances composed of discrete molecules exhibit melting and boiling points that are governed by intermolecular attractions, which are generally weaker than the forces in a network covalent structure. Understanding this distinction is key when comparing the physical properties of different inorganic compounds.

Transcript

00:01 In this problem, we're asked to compare, to make three comparisons, and their compounds with what is widely disparate melting and boiling points.

00:14 I'll give you each set of compounds, then we'll discuss them.

00:17 For a, our compounds, one of them is just an element, tungsten, and wf6.

00:27 Our melting points for each are 3422 celsius and 2 .3 celsius.

00:49 Our boiling point is 5930 and this is 17 .1.

01:04 The shape of the wf6 is trigonal bipedal.

01:23 It is non -polar.

01:29 Therefore, the intermolecular forces are london disparate.

01:34 Forces the weakest of all.

01:38 Tungsten experiences extremely effective, extremely effective 5d electron bonding and it's got like the highest melting point of all of our metals.

02:07 So let's see, those are our structures and bondings.

02:15 Our second set of compounds is so2 and sf6.

02:28 Again, let's get our melting points and our boiling points.

02:33 Our melting point is negative 72 degrees celsius and negative 21, 121 degrees celsius.

02:46 Here we have negative 10 and negative 38 degrees celsius.

02:57 The shape of so2 is bent and it's got dipole -dipole interactions for the intermolecular force.

03:10 Sf6 is csa shaped.

03:18 It is barely polar...