A Guide to the Metalloids
Explore the "stair-step" elements that bridge the gap between metals and nonmetals.
What Are Metalloids?
Metalloids, also known as semi-metals, are a unique group of elements that have properties intermediate between those of metals and nonmetals. They are found along the "stair-step" line that divides the metals from the nonmetals on the periodic table.
This group typically includes Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), and Tellurium (Te). Their ability to act as semiconductors makes them the foundation of the modern electronics industry.
Key Characteristic: Semiconductors
The most defining feature of metalloids is their ability to conduct electricity under certain conditions, but not as well as metals. This property is called being a semiconductor.
- At low temperatures, they act as insulators (like nonmetals).
- At higher temperatures or when "doped" with impurities, they can conduct electricity (like metals).
This controllable conductivity is the principle behind transistors and computer chips, making elements like Silicon and Germanium essential for all modern electronics.
Location on the Periodic Table
The metalloids form a diagonal, stair-step line separating the metals on the left from the nonmetals on the right.
Properties and Uses of Metalloids
Physically, metalloids are often brittle solids with a metallic luster.
| Element | Symbol | Key Use(s) |
|---|---|---|
| Boron | B | Borosilicate glass (Pyrex), control rods in nuclear reactors, high-strength lightweight materials. |
| Silicon | Si | The cornerstone of modern electronics: computer chips, transistors, solar cells, silicones. |
| Germanium | Ge | Fiber-optic systems, infrared optics (night-vision), wide-angle camera lenses. |
| Arsenic | As | Gallium arsenide for high-speed semiconductors, formerly in pesticides (highly toxic). |
| Antimony | Sb | Flame retardants, alloys with lead for batteries and bullets. |
| Tellurium | Te | Alloying agent to improve machinability of steel, used in some solar panels and memory chips. |
Key Takeaways
- Metalloids are located on the stair-step line between metals and nonmetals.
- They have properties intermediate between metals and nonmetals (e.g., brittle but have a metallic luster).
- Their most important property is being semiconductors, which allows for controllable electrical conductivity.
- Silicon (Si) is the most famous metalloid and is the basis for virtually all modern electronics.
Frequently Asked Questions
What makes an element a metalloid?
A metalloid is an element that has properties that are intermediate between those of metals and nonmetals. For example, they might look like a metal (shiny) but be brittle like a nonmetal. Most importantly, they are typically semiconductors.
Why are metalloids important for electronics?
Their ability to act as semiconductors is key. Unlike a metal (which always conducts electricity) or a nonmetal (which doesn't), a semiconductor's conductivity can be precisely controlled. This ability to switch conductivity on and off is the basis of all modern transistors and computer chips.
Is Silicon a metal?
No, silicon is the most famous example of a metalloid. It has a metallic luster, but it is brittle and only a partial conductor of electricity, fitting the classic definition of a metalloid.
Are all metalloids safe?
No. While silicon and germanium are relatively non-toxic, others like arsenic and antimony are famously toxic and must be handled with extreme care.