READ: Metals, Non-metals and Metalloids

READ: Metals, Non-metals and Metalloids

There are 3 classes of elements: metals, nonmetals, and metalloids. You already should know some basic properties of metals and nonmetals from your interaction with the world around you. In this section, we will look a little closer at some properties of each that you might not be familiar with.

Metals

All of the elements on the left side and in the middle of the periodic table, except for hydrogen, are metals.  In fact, the majority of elements are metals.  Below are some basic properties of metals:

• Metals have relatively high melting points. This explains why all metals except for mercury are solids at room temperature.
• Most metals are good conductors of heat and electricity. That's why metals such as iron, copper, and aluminum are used for pots and pans because they can conduct heat.
• Metals are generally shiny. This is because they reflect much of the light that strikes them.
• The majority of metals are ductile. This means that they can be pulled into long, thin shapes, like aluminum electric wires.
• Metals tend to be malleable. This means that they can be formed into thin sheets without breaking.

To understand why metals can conduct electricity, consider the metal lithium as an example. An atom of lithium is modeled below. Look at lithium's electrons. There are two electrons at the first energy level. This energy level can hold only two electrons, so it is full in lithium. The second energy level is another story. It can hold a maximum of eight electrons, but in lithium it has just one. A full outer energy level is the most stable arrangement of electrons. Lithium would need to gain seven electrons to fill its outer energy level and make it stable. It's far easier for lithium to give up its one electron in energy level 2, leaving it with a full outer energy level (now level 1). Electricity is a flow of electrons. Because lithium (like most other metals) easily gives up its "extra" electron, it is a good conductor of electricity.

Nonmetals

Elements located on the right side of the periodic table are nonmetals.  The three pure substances pictured above have the distinction of being among the top ten elements that make up the human body.  Most of the elements that comprise the human body—as well as the majority of other living things—are nonmetals.  As their name suggests, nonmetals generally have properties that are very different from the properties of metals. Properties of nonmetals include the following:

• Nonmetals have a relatively low boiling point, which explains why many of them are gases at room temperature. Some nonmetals are solids at room temperature, including the three pictured above, and one nonmetal—bromine—is a liquid at room temperature.
• Most nonmetals are poor conductors of electricity and heat. In fact, they are such poor conductors of heat that they are often used for insulation.
• Solid nonmetals are generally dull and lack the luster of metals.  
• Solid nonmetals are brittle and will easily crack and crumble.

To understand why nonmetals exhibit properties so different from metals, let's look at the electron configuration of the nonmetal fluorine as an example.  An atom of fluorine is modeled below.  What do you notice about fluorine's valance electrons in comparison to lithium's valence electrons?  Fluorine needs one more electron to fill its outer energy level in order to have the most stable arrangement of electrons. Remember that the second energy level can hold 8 electrons.  Eight valence electrons is the magic number of electrons to make stable, happy atoms.  Therefore, fluorine readily accepts an electron from any element that is equally "eager" to give one up, such as the metal lithium. It is easier for fluorine to accept (gain) 1 electron than it would be to lose 7 electrons.  An electric current is a flow of electrons. Elements that readily give up electrons (the metals) can carry electric current because their electrons can flow freely. Elements that gain electrons (the nonmetals) instead of giving them up cannot carry electric current. They hold onto their electrons so they cannot flow.

Metalloids

The smallest class of elements are metalloids. There are actually just seven metalloids. They include silicon, boron, germanium, arsenic, antimony, tellurium, and astatine. Metalloids fall between metals and nonmetals in the periodic table making a stair step arrangement. They also fall between metals and nonmetals in terms of their properties.  

Most metalloids have some physical properties of metals and some physical properties of nonmetals. For example, metals are good conductors of both heat and electricity, whereas nonmetals generally cannot conduct heat or electricity. And metalloids? They fall between metals and nonmetals in their ability to conduct heat, and if they can conduct electricity, they usually can do so only at higher temperatures. Metalloids that can conduct electricity at higher temperatures are called semiconductors. Silicon is an example of a semiconductor. It is used to make the tiny electric circuits in computer chips.

Metalloids tend to be shiny like metals but brittle like nonmetals. Because they are brittle, they may chip like glass or crumble to a powder if struck. Other physical properties of metalloids are more variable, including their boiling and melting points, although all metalloids exist as solids at room temperature.

Summary

In summary, it is important that you know where metals, nonmetals, and metalloids are found on the periodic table as well as some basic properties of each as mentioned above. Here is a periodic table that shows where each class of element is located. The metals are colored in blue, nonmetals in red, and metalloids in green.

To review the properties of metals, nonmetals, and metalloids and quiz yourself on your understanding, please click through the following animation:

 Georgia Virtual, Atomic Theory and Periodic Table, CC BY-NC-SA 3.0

After you have completed this part of the lesson, you can check the associated box on the main course page to mark it as complete