Metals, non-metals and metalloids

Metals make up more than 78% of the known elements and lie on the left of the table. Non-metals, fewer than twenty, lie at the top right.

Metals are usually solid at room temperature (mercury is liquid; gallium melts at 303 K and caesium at 302 K), with high melting and boiling points. They conduct heat and electricity and are malleable (beaten into sheets) and ductile (drawn into wires).

Non-metals are mostly gases or solids that melt and boil at low temperatures (boron and carbon are exceptions). They conduct poorly, and the solid ones are mostly brittle, neither malleable nor ductile.

Across a period, character changes from metallic to non-metallic; down a group, elements become more metallic.

The change is gradual. Elements along the diagonal zig-zag line, such as silicon, germanium, arsenic, antimony and tellurium, show properties of both and are called metalloids or semi-metals.

Worked order of increasing metallic character: P < Si < Be < Mg < Na (metallic character falls left to right and rises down a group).