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Explanation of the types of chemical bonding by Ron Kurtus - Succeed in Chemistry. Key words: physical science, compounds, molecules, atoms, elements, electrons, orbits, shells, valance, covalent, ionic, positive ions, negative, Lewis electron dot notation, School for Champions. Copyright © Restrictions

Types of Chemical Bonding

by Ron Kurtus (14 October 2005)

There are several ways in which atoms can combine or chemically bond together to form a molecule. The most common type is covalent bonding, where the atoms share pairs of outer shell or valence electrons. Covalent bonding may be single or multiple, depending on the number of pairs the atoms share.

Ionic bonding is another common way atoms combine, where one atom passes its electron to the other element, creating positive (+) and negative (-) ions. Finally, there are several other minor types of chemical bonding that will not be discussed here.

Questions you may have include:

This lesson will answer those questions.



Single covalent bonding

Most common type of chemical bonding is single covalent bonding, where one pair of valence electrons is shared by the two atoms. Valence electrons are those that are in the outer orbit or shell of an atom.

Hydrogen molecule

A good example of single covalent bonding is the Hydrogen molecule (H2).

Each Hydrogen atom shares the other's valance electron

Each Hydrogen atom shares the other's valance electron

Since the atoms are sharing the other's electron, both appear to have the first orbit or shell filled with the maximum of two electrons.

Water molecule

Another example of single covalent bonding is the water (H2O) molecule. Adding hydrogen gas molecules (H2) to oxygen gas molecules (O2) can result in an explosion if lit by a flame or spark. The end product is the very stable water molecule (H2O). The chemical equation is:

2H2 + O2 → 2H2O

The resulting molecule has single covalent bonding:

Oxygen has single covalent bonding with each of the two Hydrogen atoms

Oxygen has single covalent bonding with each of the two Hydrogen atoms

You can see that with the sharing of electrons, each Hydrogen atom has two valence electrons, thus filling their outer orbits. Likewise, Oxygen now has 8 outer orbit electrons. This makes for a good chemical bond and a stable molecule. Usually, electrolysis is required to separate the hydrogen and oxygen from water.

Multiple covalent bonding

Some molecules are held together with double, triple and even quadruple covalent bonding. That means that two, three or four pairs of electrons are shared. A vast majority of multiple covalent boding is double covalent bonding.

Double covalent bonding

Since its outer orbit is missing 2 electrons, you never see an Oxygen atom by itself, because and it can readily combine with another Oxygen atom to form a more stable Oxygen molecule (O2).

The Oxygen molecule is held together by a double covalent bonding.

Oxygen molecule employs double covalent bonding

Oxygen molecule employs double covalent bonding

The problem with this "solar system" diagram of the atoms is that sharing two paris of electrons just doesn't look right. We know it happens, but the illustration seems confusing. It gets even more confusing in molecules having triple or quadruple covalent bonding.

Electron dot notation

Thus a method to simplify a diagram of the molecule was devised. It only shows the valence electrons as dots. It is called the electron dot notation. (It is also often called the Lewis dot notation, after the person who invented it.)

Oxygen molecule in dot notation

Oxygen molecule in dot notation

Water molecule in dot notation

Water molecule in dot notation

There are a few other ways of diagramming molecules to better illustrate the covalent and even ionic bonding.

There are also a few other types of chemical bonding that are not common enough to go into in this lesson.

Ionic bonding

One type of chemical bonding is ionic bonding. In such a case, one atom will give up one or more valance electrons to the other atom. The atom losing electrons becomes a positive (+) ion and the one gaining electrons becomes a negative (-) ion. The electrical force keeps the atoms close together and bonds them into a molecule.

Sodium chloride

Salt or Sodium Chloride (NaCl) is a good example of a ionic bonding. Sodium (Na) has 1 valance electron and Chlorine (Cl) has 7 electrons in its outer orbit. If Sodium lost its valance electron, its next shell will be full. But that would also make Sodium a positive ion. If Chlorine gained 1 valance electron, its shell would be full with a maximum of 8 electrons, and it would then be a negative ion.

Thus Sodium Chloride (NaCl) is a bonding of the Na+ ion and the Cl- ion.

Sodium lets Chlorine use its valance electron

Sodium lets Chlorine use its valance electron

In its solid form as table salt, the Na+ and the Cl- ions are held in place in a crystalline lattice. When dissolved in water, the ions freely roam about the solution.

Note that the combination of these two elements can result in a violent reaction, giving off heat and perhaps even an explosion. Seldom is Na directly combined with Cl to form NaCl. Usually the combination is done indirectly with other compounds or in a water solution. But the fact that the bonding process gives off energy means that the molecule is fairly stable and not easy to separate.

Summary

Chemical bonding when atoms or molecules combine or bond together to form new material. The outer electron orbits or shells determine which elements or molecules combine and how well they bond together. Some materials will readily combine, often giving off heat energy. Other combinations are not very stable and a little heat or even vibration can cause the molecules to split apart, giving off energy.


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