Elements on the periodic table can be broadly classified into three categories: metals, nonmetals, and metalloids. Metals (found on the left and center) are typically shiny, conduct heat and electricity well, and can be bent or shaped. Nonmetals (found on the right) tend to be dull, poor conductors, and brittle as solids. Metalloids (along the staircase boundary) have properties somewhere in between, which makes them useful in electronics as semiconductors.
Examine real samples or images of elements from each category — iron or copper (metals), sulfur or carbon (nonmetals), silicon (metalloid). Test or discuss conductivity, luster, and flexibility. Then locate each on the periodic table to see the spatial pattern.
The periodic table contains more than 100 elements, but you can start making sense of them by sorting them into three broad categories: metals, nonmetals, and metalloids. This classification is based on physical and chemical properties, and the periodic table is arranged so you can see the grouping at a glance.
Metals make up the majority of elements — roughly three-quarters of the periodic table. They occupy the left side and the middle of the table. You are surrounded by metals every day: iron in bridges, copper in electrical wires, aluminum in soda cans, gold in jewelry. Most metals share a set of recognizable properties. They are shiny (lustrous) when polished. They conduct heat and electricity very well, which is why copper and aluminum are used in wiring and cookware. They are malleable (can be hammered into sheets) and ductile (can be drawn into wires). Most metals are solids at room temperature, with mercury being the notable exception — it is a liquid.
Nonmetals are found on the right side of the periodic table. They include familiar elements like oxygen, nitrogen, carbon, and sulfur. Nonmetals tend to have the opposite properties of metals: they are usually dull, poor conductors of heat and electricity, and brittle when solid. Many nonmetals are gases at room temperature (oxygen, nitrogen, helium), a few are solids (carbon, sulfur, phosphorus), and one — bromine — is a liquid. Despite being fewer in number, nonmetals are incredibly important. Oxygen and nitrogen make up almost all of the air you breathe, and carbon is the backbone of every living molecule.
Metalloids occupy a narrow band along the staircase-shaped boundary between metals and nonmetals. Elements like silicon, germanium, boron, and arsenic fall in this zone. They have some properties of metals and some of nonmetals. The most important property of metalloids is that they are semiconductors — they conduct electricity better than nonmetals but not as well as metals. This makes them essential for modern electronics. Silicon, the second most abundant element in Earth's crust, is the basis of nearly every computer chip and solar cell in the world.
Knowing whether an element is a metal, nonmetal, or metalloid gives you an instant set of predictions about how it behaves. When you see an unfamiliar element on the periodic table, just check which side of the staircase it falls on, and you already know a great deal about its physical and chemical personality.