The Periodic Table: Metals, Nonmetals, and Metalloids
The periodic table classifies every known element into one of three categories: metals, nonmetals, or metalloids. This classification is based on a stair-stepped line running through the table, and it tells you a lot about how an element behaves—whether it conducts electricity, how it reacts with other elements, and even what it looks and feels like. Using the periodic table, you can classify elements in many ways, and this metal/nonmetal/metalloid system is one of the most useful. The periodic table is also organized in families and periods.
What are metals in the periodic table?
Metals are the elements found to the left of the stair-stepped line that runs from Boron (B), atomic number 5, down to Polonium (Po), atomic number 84. Except for Germanium (Ge) and Antimony (Sb), every element to the left of that line is classified as a metal.
Metals share properties you likely already associate with the metals you encounter in everyday life:
- They are solid at room temperature (with the exception of mercury, Hg, which is a liquid).
- They are shiny, and they conduct electricity and heat well.
- They are ductile, meaning they can be drawn into thin wires.
- They are malleable, meaning they can be hammered into very thin sheets.
Metals also tend to lose electrons easily during chemical reactions, which explains much of their reactivity. The following figure shows the metals.
What are nonmetals in the periodic table?
Nonmetals are the elements found to the right of the stair-stepped line (along with hydrogen), excluding the elements that border the line itself. Nonmetals have properties that are essentially the opposite of metals.
Where metals are ductile and malleable, nonmetals are brittle and break rather than bend. Nonmetals are also poor conductors of both heat and electricity, and they tend to gain electrons during chemical reactions rather than lose them. Some nonmetals exist as liquids, and others as gases, showing more variety in physical state than metals do. These elements are shown in the following figure.
What are metalloids in the periodic table?
Metalloids, also called semimetals, are the elements that sit directly along the stair-stepped line dividing metals from nonmetals. As their in-between position suggests, metalloids have properties that blend characteristics of both metals and nonmetals.
Metalloids are especially important economically because of their unique conductivity: they only partially conduct electricity, a property known as semiconductivity. This makes metalloids like silicon essential to the semiconductor and computer chip industry that powers modern electronics. The metalloids are shown in the following illustration.
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