4.6. Chemical Bonds: Intermolecular Forces

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Chemical bonds are a fundamental part of the study of chemistry and are essential for understanding the structure and properties of substances. In the context of the ENEM, it is important to have a clear understanding of chemical bonds, including intermolecular forces.

Chemical bonds occur when atoms share, donate, or accept electrons to reach a more stable state. There are three main types of chemical bonds: ionic, covalent, and metallic.

The ionic bonds occur when an atom donates one or more electrons to another atom, resulting in the formation of positive and negative ions. These ions then attract each other to form an ionic bond. Common examples of ionic compounds include table salt (NaCl) and magnesium chloride (MgCl2).

The covalent bonds occur when two atoms share one or more pairs of electrons. This usually happens between non-metallic atoms. Examples of covalent compounds include water (H2O) and carbon dioxide (CO2).

Metallic bonds occur between metal atoms, where electrons are free to move throughout the metal, resulting in properties such as electrical and thermal conductivity.

In addition to these primary bonds, there are also intermolecular forces, which are the forces of attraction between molecules. They are much weaker than ionic, covalent and metallic bonds, but still play an important role in determining the physical properties of substances, such as melting point, boiling point and solubility.

There are three main types of intermolecular forces: dipole-dipole, induced dipole, and hydrogen bonds.

The dipole-dipole forces occur between polar molecules, which have an uneven distribution of electrical charge. A common example is hydrogen chloride (HCl), where the chlorine atom attracts electrons more strongly than the hydrogen atom, resulting in a polar molecule.

The induced dipole forces, also known as London forces or van der Waals forces, occur between non-polar molecules. They are caused by temporary fluctuations in the distribution of electrons, which induce a temporary polarity in molecules. An example is helium (He), which is a non-polar molecule but can still have induced dipole forces.

Hydrogen bonds are a special type of dipole-dipole force that occurs when a hydrogen atom is bonded to a nitrogen, oxygen, or fluorine atom and is attracted to another nitrogen atom , oxygen or fluorine. Water (H2O) is a common example of a molecule that forms hydrogen bonds.

In summary, understanding chemical bonds and intermolecular forces is crucial to understanding chemistry at a deeper level. They are the basis for the structure and properties of substances and are an important topic for the Enem test.

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514.7. Chemical Bonds: Van der Waals Forces