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When viewed from some orientations, some solids have a network character, whereas when viewed from other directions they have a more molecular character.
Carbon serves as a paradigm example once more, because the form of carbon known as graphite is composed of a stack of sheets of hexagonal rings of carbon atoms stacked on top of one another.
Molecular solids can be made up of single atoms, diatomic molecules, and/or polyatomic molecular structures.
In crystalline materials, the crystal lattice structure is determined by the intermolecular interactions that exist between the constituents of the substance.
Involvement in van der Waals and London dispersion forces is possible for all atoms and molecules (sterics).
Materials have distinct features because of the absence or presence of additional intermolecular interactions that make an atom or molecule unique.
Molecular Solids
Molecular solids, which are solids made up of individual molecules, have also been discussed in the section on intermolecular forces, where the architectures of molecular solids were also discussed.
They are bound together by hydrogen bonds (if they are capable of forming them), dispersion forces, and other dipolar forces, which are listed in decreasing order of importance, and the molecules stack together in a configuration that reduces their total energy.
Ice, in which hydrogen bonding is of paramount importance, and polyethylene, in which dispersion forces are dominating, are both examples of such materials.
In general, molecular solids are soft and have low melting temperatures because the interactions between the molecules are easily overcome unless hydrogen bonds are present (in which case they behave similarly to ionic solids in terms of brittleness).
Polar Solids
The geometry of these solids is such that one side has a negative charge and the other side has a positive charge on the same side.
The dipole — dipole force of attraction – that holds them together is the driving force.
Their melting and boiling temperatures are higher than those of non-polar molecular solids, but they are still comparatively low compared to other solids.
Polar compounds include ethanol and ammonia, to name a couple of examples.
Polar molecules are formed when two atoms do not share electrons equally in a covalent link, resulting in a polar molecule.
An electric dipole is formed, with one part of the molecule carrying a little amount of positive charge and the other part carrying a small amount of negative charge.
This occurs when there is a disparity in the electronegativity levels of the two atoms in a compound molecule.
A severe difference results in the formation of an ionic bond, whereas a lesser difference results in the formation of a polar covalent bond.
Thanks to the existence of electronegativity tables, you may easily determine whether or not atoms are more or less likely to form polar covalent bonds.
If the difference in electronegativity between the two atoms is between 0.5 and 2.0, the atoms create a polar covalent connection between themselves.
If the difference in electronegativity between the atoms is larger than 2.0, the bond is said to be ionic.
Ionic chemicals are strongly polar molecules, as is the case with most organic compounds.
Illustrations of Polar Molecules
Water – H2O Ammonia – NH3 Sulphur dioxide – SO2 Hydrogen sulphide – H2S Ethanol – C2H6O Sulfur dioxide – SO2 Hydrogen sulphide – H2S
It is important to remember that ionic substances, such as sodium chloride (NaCl), are polar.
However, most of the time when people talk about “polar molecules,” they are referring to “polar covalent molecules,” and not all sorts of compounds that have polarity are considered.
When referring to the polarity of a chemical, it is advisable to prevent misunderstanding by referring to them as nonpolar, polar covalent, and ionic.
Non- Polar Solids
Because such solids contain a symmetrical distribution of electrons, there is no excess charge on any side of the solid.
Charges that are diametrically opposed cancel each other out. Methane, chlorine, hydrogen, and oxygen are just a few examples.
They are either liquids or gases at standard room temperature and pressure.
Vander Waals forces are the forces that hold the molecules in these solids together by holding them through weak dispersion or London forces.
In comparison to ionic or covalent bonds, these forces are weaker.
The absence of a net electrical charge across a molecule occurs when molecules share electrons in an equal number in a covalent link.
In a nonpolar covalent bond, the electrons are dispersed uniformly throughout the bond.
When two or more atoms have the same or similar electronegativity, it is possible to anticipate that nonpolar molecules will form.
In general, if the difference in electronegativity between two atoms is less than 0.5, the bond is called nonpolar, despite the fact that the only genuinely nonpolar molecules are those created with identical atoms (which are the exception).
Nonpolar molecules can also be formed when atoms that share a polar link arrange themselves in such a way that their electric charges cancel out each other.
Illustrations of Nonpolar Molecules
Any of the noble gases, including: He, Ne, Ar, Kr, and Xe are all pronouns.
Any of the following diatomic elements with a homonuclear nucleus:
H2, N2, O2, Cl2 are all elements (These are truly nonpolar molecules.)
Carbon dioxide (CO2) is a gas that exists in the atmosphere.
Benzene (C6H6) is a chemical compound.
Carbon tetrachloride (CCl4) is a chemical compound.
Methane is represented by the symbol CH4 and ethylene is represented by the symbol C2H4.
Conclusion
The intermolecular forces in these types of materials are dominated by strong hydrogen bonding.
When compared to polar and nonpolar molecular solids, their boiling and melting temperatures are significantly higher.
At room temperature and pressure, they exist as volatile liquids or soft solids, respectively.
The hydrogen bond is the most significant of all the directed intermolecular interactions since it is the most stable of all.
In a wide range of chemical systems spanning from inorganic to biological, it is used to determine molecular conformation, molecular aggregate formation, and the function of the molecules involved.
It is possible for hydrogen bonds to form when an electronegative atom attracts a hydrogen atom through dipole-dipole attraction.
A hydrogen bond is formed between hydrogen and fluorine, oxygen or nitrogen in the majority of cases.
Sometimes the bonding is intramolecular, or between the atoms of a single molecule, rather than between the atoms of two or more different molecules (intermolecular).
