Metalloid

A metalloid is an element with properties in between those of metals and non-metals, such as silicon; metalloids lie along the diagonal staircase that divides the two. Malay: metaloid · Chinese: 准金属.

The periodic table divides broadly into metals on the left and non-metals on the right, but the boundary is not a sharp line. The elements that fall along the diagonal staircase separating the two, silicon and boron are the examples most often quoted, show a mixture of behaviour. They may look shiny like a metal yet be brittle like a non-metal, and they often conduct electricity only weakly, which is why several of them are called semiconductors and matter so much in electronics.

Example. Silicon is the classic metalloid. It has a shiny, metal-like appearance but is brittle and a much poorer conductor than a true metal such as copper. This half-and-half behaviour is exactly why it is placed among the metalloids rather than with the metals or the non-metals, and why it is used to make computer chips. Boron behaves the same way, sitting on the borderline and sharing that mixed character, so both are named as metalloids rather than forced into one camp.

Confusion to avoid. A metalloid is not simply “a weak metal” or “a bad non-metal”, it is an element whose properties genuinely sit between the two categories. Do not classify silicon as a metal just because it looks shiny, and remember that most elements are still clearly metals or clearly non-metals; only the handful along the staircase are metalloids. It also helps to remember that whether an element is a metal, a metalloid or a non-metal is decided by its properties, not merely by which side of the table it appears to be on.

In the Periodic Table of Elements chapter the metalloid completes the metal-to-non-metal picture: reading across a period the character shifts from metal, through metalloid, to non-metal, and the metalloid is the bridge that makes that gradual change visible.