Chemical Bonding

General Chemistry Index

Where are we going with this? This page will give the ability to use laboratory observations and data to compare and contrast ionic, covalent, network, metallic, polar, and non-polar substances with respect to constituent particles, strength of bonds, melting and boiling points, and conductivity; provide examples of each type.

Chemical Bonding
About those compounds… 

Compounds are formed when two or more different elements combine chemically in fixed, specific ratios. Combine… What?

Elements combine to form compounds by chemically bonding to other elements—in fixed, specific ratios. They do this in several ways, both intramolecularly (strong) and intermolecularly (weaker).  (See also.)

So what do we mean by bonding? A chemical bond is a force that holds atoms together in a molecule or compound.

Bonds are formed when valence electrons, the electrons in the outermost outermost occupied energy level of an atom. interact.  (See also.) 

It is very important to keep in mind that atoms are most stable when they have eight electrons in their valence shell. This is sometimes called the octet rule.

The octet rule is a useful guideline, but it is not universal. For example, hydrogen becomes stable with only two electrons.

More fundamentally, bonds form when the bonded arrangement produces a lower-energy, more stable system. The octet rule helps us predict many of the bonding arrangements that result.

There are several types of intramolecular bonds.

Ionic bonding occurs when two ions are attracted to each other after one atom has transferred its electron(s) to another. This is usually between a metal and a non-metal. This is an intramolecular bond. 

Covalent bonding occurs between two atoms and takes place within the electron orbitals such that full sets of orbitals can be created (octet rule). This usually takes place between two nonmetals that are sharing electrons. This is an intramolecular bond.

Polar covalent bonding occurs when two atoms combine covalently, but when one of them has a higher electronegativity. Polar covalent bonding usually occurs between nonmetals. This is an intramolecular bond.

Metallic bonding occurs between metal atoms. The valence electrons are free to move throughout the metal, forming a “sea of electrons” around positively charged metal ions. The attraction between the positive ions and the moving electrons holds the metal together. This helps explain why metals are usually good conductors of heat and electricity and are often malleable and ductile. 

 

Intermolecular bonding… 

In addition to the chemical bonds that hold atoms together, molecules can also attract neighboring molecules.

These attractions are called intermolecular forces.

Intermolecular forces are generally weaker than ionic and covalent bonds because they occur between molecules rather than holding the atoms of a molecule together.

Hydrogen bonding is an intermolecular attraction which occurs when a hydrogen atom bonded to a strongly electronegative atom exists in the vicinity of another electronegative atom with a lone pair of electrons.

Dipole-dipole interactions are intermolecular attractions that occur when the partially positively charged part of a molecule interacts with the partially negatively charged part of the neighboring molecule.  

London dispersion forces result from intermolecular attraction between compounds resulting from the occasional, random non-uniform distribution of electrons as they move around.

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