INTERATOMIC LINKS: CHARACTERISTICS AND TYPES - CHEMISTRY - 2024

The interatomic bond is the chemical bond that forms between atoms to produce molecules. Although today scientists generally agree that electrons do not revolve around the nucleus, throughout history it was thought that each electron orbited around the nucleus of an atom in a separate shell.

Today, scientists have concluded that electrons hover over specific areas of the atom and do not form orbits, yet the valence shell is still used to describe the availability of electrons.

Figure 1: atoms interacting with each other through chemical bonds.

Linus Pauling contributed to the modern understanding of chemical bonding by writing the book "The Nature of Chemical Bonding" where he collected ideas from Sir Isaac Newton, Étienne François Geoffroy, Edward Frankland and in particular Gilbert N. Lewis.

In it, he linked the physics of quantum mechanics with the chemical nature of the electronic interactions that occur when chemical bonds are made.

Pauling's work concentrated on establishing that true ionic bonds and covalent bonds lie at the ends of a bond spectrum, and that most chemical bonds are classified between those extremes.

Pauling further developed a bond-type sliding scale governed by the electronegativity of the atoms involved in the bond.

Pauling's immense contributions to our modern understanding of chemical bonding led to his being awarded the 1954 Nobel Prize for "research into the nature of chemical bonding and its application to elucidating the structure of complex substances."

Living things are made up of atoms, but in most cases, those atoms don't just float individually. Instead, they are normally interacting with other atoms (or groups of atoms).

For example, atoms can be connected by strong bonds and organized into molecules or crystals. Or they can form temporary, weak bonds with other atoms that collide with them.

Both the strong bonds that bind molecules and the weak bonds that create temporary connections are essential to the chemistry of our bodies and to the existence of life itself.

Atoms tend to organize themselves in the most stable patterns possible, which means they have a tendency to complete or fill their outermost electron orbits.

They bond with other atoms to do just that. The force that holds atoms together in collections known as molecules is known as a chemical bond.

Types of interatomic chemical bonds

Metallic bond

The metallic bond is the force that holds the atoms together in a pure metallic substance. Such a solid consists of tightly packed atoms.

In most cases, the outermost electron shell of each of the metal atoms overlaps with a large number of neighboring atoms. As a consequence, valence electrons continually move from atom to atom and are not associated with any specific pair of atoms.

Figure 2: illustration of a metallic bond

Metals have several qualities that are unique, such as the ability to conduct electricity, low ionization energy, and low electronegativity (so they give up electrons easily, that is, they are cations).

Their physical properties include a shiny (glossy) appearance, and they are malleable and ductile. Metals have a crystalline structure. However, metals are also malleable and ductile.

In the 1900s, Paul Drüde came up with the electron sea theory by modeling metals as a mixture of atomic nuclei (atomic nuclei = positive nuclei + inner electron shell) and valence electrons.

In this model, the valence electrons are free, delocalized, mobile, and not associated with any particular atom.

Ionic bond

Ionic bonds are electrostatic in nature. They occur when an element with a positive charge joins one with a negative charge by coulombic interactions.

Elements with low ionization energies have the tendency to lose electrons easily while elements with high electron affinity have the tendency to gain them producing cations and anions respectively, which are what form ionic bonds.

Compounds showing ionic bonds form ionic crystals in which positive and negatively charged ions oscillate close to each other, but there is not always a direct 1-1 correlation between positive and negative ions.

Ionic bonds can typically be broken through hydrogenation, or the addition of water to a compound.

Substances held together by ionic bonds (such as sodium chloride) can commonly separate into true charged ions when an external force acts on them, such as when dissolved in water.

Furthermore, in solid form, individual atoms are not attracted to an individual neighbor but instead form giant networks that are attracted to each other by electrostatic interactions between the nucleus of each atom and neighboring valence electrons.

The attractive force between neighboring atoms gives ionic solids an extremely orderly structure known as an ionic lattice, where oppositely charged particles align with each other to create a tightly bound rigid structure.

Figure 3: sodium chloride crystal

Covalent bond

Covalent bonding occurs when pairs of electrons are shared by atoms. Atoms will bond covalently with other atoms to gain more stability, which is achieved by forming a complete electron shell.

By sharing their outermost (valence) electrons, atoms can fill their outer shell with electrons and gain stability.

Figure 4: Lewis diagram of the covalent bond of the nitrogen molecule

Although atoms are said to share electrons when they form covalent bonds, they often do not share electrons equally. Only when two atoms of the same element form a covalent bond are the shared electrons actually shared equally between the atoms.

When atoms of different elements share electrons through covalent bonding, the electron will be drawn further towards the atom with the highest electronegativity resulting in a polar covalent bond.

When compared to ionic compounds, covalent compounds usually have a lower melting and boiling point and have less tendency to dissolve in water.

Covalent compounds can be in a gas, liquid, or solid state and do not conduct electricity or heat well.

Hydrogen bonds

Figure 5: hydrogen bonds between two water molecules

Hydrogen bonds or hydrogen bonds are weak interactions between a hydrogen atom attached to an electronegative element with another electronegative element.

In a polar covalent bond that contains hydrogen (for example, an OH bond in a water molecule), the hydrogen will have a slight positive charge because the bonding electrons are pulled more strongly towards the other element.

Due to this slight positive charge, hydrogen will be attracted to any neighboring negative charges.

Links to Van der Waals

They are relatively weak electrical forces that attract neutral molecules to each other in gases, in liquefied and solidified gases, and in almost all organic and solid liquids.

The forces are named for the Dutch physicist Johannes Diderik van der Waals, who in 1873 first postulated these intermolecular forces in developing a theory to explain the properties of real gases.

Van der Waals forces is a general term used to define the attraction of intermolecular forces between molecules.

There are two classes of Van der Waals forces: the London Scattering Forces that are weak and stronger dipole-dipole forces.

References

1. Anthony Capri, AD (2003). Chemical Bonding: The Nature of the Chemical Bond. Retrieved from visionlearning visionlearning.com
2. Camy Fung, NM (2015, August 11). Covalent Bonds. Taken from chem.libretexts chem.libretexts.org
3. Clark, J. (2017, February 25). Metallic Bonding. Taken from chem.libretexts chem.libretexts.org
4. Encyclopædia Britannica. (2016, April 4). Metallic bond. Taken from britannica britannica.com.
5. Encyclopædia Britannica. (2016, March 16). Van der Waals forces. Taken from britannica britannica.com
6. Kathryn Rashe, LP (2017, March 11). Van der Waals Forces. Taken from chem.libretexts chem.libretexts.org.
7. Khan, S. (SF). Chemical bonds. Taken from khanacademy khanacademy.org.
8. Martinez, E. (2017, April 24). What is Atomic Bonding? Taken from sciencing sciencing.com.
9. Wyzant, Inc. (SF). Bonds. Taken from wyzant wyzant.com.