Metals, nonmetals & metalloids

The first classification every chemistry student learns — and the staircase line that draws it.

Before categories like "transition metal" or "halogen," there is a simpler, older split: every element is a metal, a nonmetal, or something in-between called a metalloid. On the interactive table, the Type filter buttons highlight each class instantly. Of the 118 known elements, 92 count as metals, 20 as nonmetals, and 6 as metalloids — the metals win by a landslide.

Metals: the big league

Metals dominate the left and center of the table — from the explosive sodium to the noble gold. Despite that range, they share a family signature:

• Luster — freshly cut or polished, they shine.
• Conductivity — they carry electricity and heat well; silver and copper are the best of all.
• Malleability and ductility — they bend, roll, and draw into wire instead of shattering. A gram of gold can be beaten into a sheet a square meter across.
• They lose electrons in reactions, forming positive ions. This is the chemical definition — the others follow from it, because freely wandering electrons are exactly what makes a material shiny, conductive, and bendable.
• Mostly solid — every metal is solid at room temperature except mercury, the famous liquid metal (and gallium and caesium melt just above it, around 30 °C).

Within the metals, character varies enormously: compare a soft alkali metal you could cut with a butter knife (potassium) to tungsten, which holds the highest melting point of any metal at 3,422 °C, or osmium, the densest naturally occurring element.

Nonmetals: few but essential

The 20 nonmetals crowd the upper right of the table — plus hydrogen, the eternal special case parked over the metals in group 1. Nonmetals are close to the opposite of metals in every column of the checklist:

• Dull and brittle when solid — think of sulfur's crumbly yellow lumps or the graphite in a pencil (carbon).
• Poor conductors — most are insulators.
• They gain or share electrons, forming negative ions or covalent molecules.
• Many are gases at room temperature — oxygen, nitrogen, the halogens fluorine and chlorine, and all the noble gases. Bromine is the lone nonmetal liquid.

What nonmetals lack in numbers they make up in importance: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur are the six elements life is chiefly built from.

Metalloids: the staircase six

Between the two camps runs a diagonal "staircase" line, and hugging it are six elements that refuse to pick a side: boron, silicon, germanium, arsenic, antimony, and tellurium.

Metalloids typically look metallic — silicon has a handsome gray sheen — but behave halfway: they are brittle like nonmetals and conduct electricity only modestly. That lukewarm conductivity turns out to be the most economically important property on the periodic table. A semiconductor can be switched between conducting and insulating, and that switch is the transistor — the building block of every chip. Silicon runs the computer age; germanium ran its opening act in the first transistors of the 1940s and 50s.

Reading the boundary

Metallic character isn't on/off — it fades gradually along the table's main diagonal. That gives you two rules of thumb:

• Down a group, elements get more metallic. Group 14 runs from nonmetal carbon, through metalloids silicon and germanium, to genuine metals tin and lead — the whole classification in a single column.
• Across a period, elements get less metallic — period 3 slides from sodium and magnesium (metals) through silicon (metalloid) to phosphorus, sulfur, and chlorine (nonmetals).

This is the same bottom-left → top-right arrow behind every periodic trend: metallic character falls as electronegativity and ionization energy climb.

Quick self-test

Cover the table and classify these five: barium, iodine, arsenic, nickel, xenon. (Metal, nonmetal, metalloid, metal, nonmetal.) Then check yourself on the interactive table with the Type filters — or read any element's classification on its reference page, like arsenic's. For what the classes mean chemistry-wise group by group, continue to the element families tour.