When you think of metals, do you think of solid objects such as iron nails and gold jewelry? If so, it might surprise you to learn that the shiny liquid pouring out of the pipette in the photo below is also a metal. It's called mercury, and it's the only metal that normally exists on Earth as a liquid. Just what are metals, and what are their properties? Read on to find out.
Figure 6.5.1: Liquid mercury.
What Are Metals?
Metals are elements that can conduct electricity. They are one of three classes of elements (the other two classes are nonmetals and metalloids). Metals are by far the largest of the three classes. In fact, most elements are metals. All of the elements on the left side and in the middle of the periodic table, except for hydrogen, are metals. There are several different types of metals, including alkali metals in group 1 of the periodic table, alkaline Earth metals in group 2, and transition metals in groups 3 - 12. The majority of metals are transition metals.
Properties of Metals
Elements in the same class share certain basic similarities. In addition to conducting electricity, many metals have several other shared properties, including those listed below.
- 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. That's why metals such as iron, copper, and aluminum are used for pots and pans.
- Metals are generally shiny. This is because they reflect much of the light that strikes them. The mercury pictured above is very shiny.
- The majority of metals are ductile. This means that they can be pulled into long, thin shapes, like the aluminum electric wires in the figure below.
- Metals tend to be malleable. This means that they can be formed into thin sheets without breaking. An example is aluminum foil, also pictured in the figure below.
Figure 6.5.2: Aluminum, like most metals, is both ductile and malleable.
Explaining the Properties of Metals
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. This tendency to give up electrons also explains other properties of metals such as lithium.
Figure 6.5.3: Model of lithium atom.
- Metals are elements that can conduct electricity. Most elements are metals.
- All metals except for mercury are solids at room temperature. Many metals are shiny, ductile, and malleable. Most are also good conductors of heat.
- Electricity is a flow of electrons. Atoms of metals tend to give up electrons, explaining why they are good conductors of electricity. The tendency to give up electrons also explains many of the other properties of metals.
At the following URL, click on any one of the metals in the interactive periodic table. Read the information provided about your choice metal, and then make a poster demonstrating its structures, properties, and uses.
CK-12 Foundation by Sharon Bewick, Richard Parsons, Therese Forsythe, Shonna Robinson, and Jean Dupon.