Families of Elements
To help understand the overall arrangement of the table, it is helpful to divide it into two groups; metals and nonmetals. Metals are usually typified by shiny, malleable, ductile substances that are eager to loose electrons. Conversely, nonmetals are brittle and try to gain electrons. The lower and further left on the table that one looks, the more the elements act like metals, while the higher and further right on the table one moves, the more the elements become nonmetals. In the center is a region of semimetallic compounds known as the metaloids. These can exhibit properties of both metals and nonmetals. Also, there are special cases on the table. Starting with period four, a group of elements appear. These are called the transition metals and all have very similar properties. This large collection of elements correspond to the filling of the D orbitals. Beginning in period six, there appears another collection of elements known as the rare earths or actinides. Their appearance here reflects the filling of the F orbitals. All of these metals have extremely similar chemical properties and are also very scarce.
Moving from these rather rare elements to ones that are encountered each day, let us look at the leftmost column of the chart. This group contains the family known as the alkali metals. This family is characterized by extremely reactive soft metals that will tend to form +1 ions. The family to their right are the alkaline earth metals. These are similar but tend to form a +2 ion.
Moving across the chart to the rightmost column, we find the family of elements known as the noble gasses. This family is characterized by their lack of reactivity. Each member of the group has a full outer shell and so is not interested in acquiring or losing electrons. These gasses are satisfied. The next column to the left contains the family known as the halogens. This family is the most reactive group of elements known. The members of this family are eager to acquire one electron and become anions with a -1 charge.
Other families on the chart are also grouped together but because their chemical and physical reactions are complex, it is difficult to make general statements about them. Those elements in the family headed by oxygen usually try to form -2 ions, those under nitrogen form -3 ions, and those under carbon form the unique group which can either be +4 or -4 ions.
Carbon is of particular interest because of its ability to combine with almost every other element as well as itself to form long chains or polymers. A polymer is a large molecule composed of a repeating sequence of chemicals bonded together.
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