Chemical Bonding - You can see why you must be able to visualize the distribution of electrons in an atom, especially the valence electrons, since their number determines how one atom will react with another. What happens when an atom with only one energy level has less than two electrons, or when an atom with two or more energy levels has less than eight electrons? How does an atom achieve a stable electron configuration?
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| Chemical Bonding |
To achieve stability, atoms unite with other atoms. Sometimes two atoms of the same element join together to form a molecule of that element. In biology, one of the most important of such molecules is hydrogen. A hydrogen molecule is indicated by the notation H2. The subscript following the symbol indicates the number of atoms in the molecule.
When the atoms of two or more elements combine chemically in a definite ratio, they form a compound. For instance, two hydrogen atoms and an oxygen atom produce the compound we know as water (H2O). When atoms combine to form compounds, they do so in a specific way, according to their valence electrons. The compounds formed by the elements have different chemical properties than the elements have when functioning alone.
In order to form compounds, atoms are held together with chemical bonds. How do chemical bonds form, and what are they? Chemical bonds are not actually objects. Instead they represent an energy relationship between the atoms involved in a compound. Bonds describe what is called the "attractive force" between two or more atoms.
The attractive force is the glue that holds the atoms together. At some time you may have done some playing around with iron filings and magnets. If you spread the filings over a piece of paper and then put the magnet under the paper, the filings respond to the attraction of the magnet by making a design on the paper. If you put two magnets beneath the paper, the patterns made by the magnetized filings allow you to see how the magnets are attracting each other. Those patterns are a concrete example of the attractive forces between the magnets at work.
The chemical bonds between atoms are similar to the patterns of those iron filings. They are electrostatic attractions between one or more atoms. There are two types of chemical bonds between atoms that are important in biology: the ionic bond and the covalent bond. (Source: Avila, Vernon L. Biology : Investigating Life On Earth Jones and Bartlett/Bookmark Series in Biology)
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