Physical Properties
Metals are generally solid at room temperature (except mercury), lustrous, malleable (can be beaten into thin sheets), ductile (can be drawn into wires), and are excellent conductors of heat and electricity. Non-metals can be solid, liquid (bromine), or gas. They are generally non-lustrous (except iodine), brittle, non-ductile, and poor conductors of heat and electricity (except graphite, a conductor).
Chemical Properties
Metals are electropositive; they tend to lose electrons to form positive ions (cations). When metals burn in air, they combine with oxygen to form basic metal oxides (e.g., 2Mg + O₂ → 2MgO). Some metal oxides, like aluminum oxide, exhibit both acidic and basic behavior and are called amphoteric oxides. Non-metals are electronegative; they tend to gain electrons to form negative ions (anions). They react with oxygen to form acidic or neutral oxides.
The Reactivity Series
The reactivity series is a list of metals arranged in decreasing order of their reactivities. Potassium (K) and Sodium (Na) are at the top and are highly reactive—they catch fire if kept in the open. Gold (Au) and Platinum (Pt) are at the bottom and are very unreactive. A more reactive metal can displace a less reactive metal from its salt solution.
Metallurgy: Extraction of Metals
The process of extracting metals from their ores and refining them is called metallurgy. Metals at the bottom of the activity series are unreactive and are found in a free state. Metals in the middle are extracted from their oxide, sulfide, or carbonate ores using reduction methods (often using carbon). Metals at the top are extracted via electrolytic reduction. The extracted metals are then refined (purified), commonly through electrolytic refining.
Corrosion and Alloys
Corrosion is the gradual destruction of metals by the action of air, moisture, or chemicals (e.g., rusting of iron, tarnishing of silver). Corrosion can be prevented by painting, oiling, galvanizing (coating with zinc), or alloying. An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal, designed to improve properties like strength and resistance to corrosion (e.g., Steel, Brass, Bronze).