Definition of Chemical Bonding

Chemical bonding provides the energy necessary to hold two different atoms together as part of a chemical compound. Covalent bonds, ionic bonds, hydrogen bonds and bonds created through the van der Waals force make up the major types of bonds in chemical compounds. These bonds vary in strength electronegativity and ionization energy.

Covalent Bonds

A covalent bond occurs when two atoms come together and share a pair of electrons, thus completing their valence shell of electrons. Covalent bonds can exist as either a polar or non-polar covalent bond. Polar covalent bonds can further form hydrogen bonds and exhibit hydrophilicity (water-loving), while non-polar covalent bonds exhibit hydrophobicity (water-fearing).

Covalent bonds in a biological system usually remain intact, without the aid of an enzyme.

Ionic Bonds

Ionic bonds occur in nature between two elements with a mutal attraction to one another. Sodium and chloride form one of the most common ionic bonded compounds in nature, NaCl, table salt. In this example, sodium and chloride share an attraction due to the valence electron shell. In sodium, one electron exists in the valence shell. In chloride, seven electrons exist in the valence shell. Elements prefer to exist in a state with a full valence shell (eight electrons), for stability. Sodium loses one electron and chloride gains one electron to put them both in their most stable state.

Ionic bonds are weaker than covalent bonds, but still relatively strong compared with other chemical bonds.

Hydrogen Bonds

The most common form of hydrogen bond occurs between the hydrogen molecule and the oxygen molecule in water, H2O. In this example, hydrogen exhibits a partial positive charge, while oxygen exhibits a partial negative charge. The electromagnetic force between them draws them together into a relatively stable compound. This bond is only about one-tenth as strong as the covalent bond.

Van Der Waals Bonds

The previous examples dealt with the forces between atoms within an element. But what happens when many of these compounds that result from bonding come together in a solution or other material? In many cases, intermolecular forces within these compounds cause each of the compounds to exhibit an overall polarity. While the compound may not have an overall net charge, uneven charge distribution throughout the molecule results in attraction of compounds to one another.

Bond Energy

Chemical bonds that form do so at differing strengths (or, bond energies) based on the electronegativity of the atoms involved. Atoms like carbon (C), hydrogen (H), nitrogen (N) and oxygen (O) consistently form bonds and break to form new compounds. The carbon-oxygen double bond, as seen in carbon dioxide (CO2), has the highest bond energy (hardest to break) of these atoms. The carbon-nitrogen single bond has the lowest bond energy (easiest to break).

References

• City University of New York: Covalent Bonds
• Elmhurst College: Hydrogen Bonds
• Kimball's Biology: Bond Energy

Resources

• W.H. Freeman: Chemical Bond Formation