Metals and Non-metals

Metals are generally lustrous (shiny), malleable (can be beaten into sheets), ductile (can be drawn into wires), and good conductors of heat and electricity. They are sonorous (produce a ringing sound when struck) and generally have high melting and boiling points. However, there are notable exceptions: mercury is a liquid metal at room temperature; gallium and caesium have very low melting points (melt in your palm); sodium and potassium are so soft they can be cut with a knife; and iodine is a non-metal that is lustrous. Non-metals are generally brittle, poor conductors, and have lower melting points. Carbon in the form of diamond is the hardest natural substance, and graphite (also carbon) is a good conductor of electricity despite being a non-metal.

Metals react with oxygen to form metal oxides (mostly basic). The vigour of reaction varies: potassium and sodium catch fire in water; magnesium burns with a bright white flame; iron reacts slowly; gold and silver do not react. The reactivity series arranges metals in decreasing order of reactivity: K > Na > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > [H] > Cu > Hg > Ag > Au > Pt. A more reactive metal can displace a less reactive metal from its salt solution. Metals above hydrogen in the series react with dilute acids to produce hydrogen gas; metals below hydrogen (Cu, Ag, Au) do not react with dilute acids. Aqua regia (3:1 mixture of conc. HCl and conc. HNO3) can dissolve gold and platinum.

The method of extraction depends on the metal's position in the reactivity series. Highly reactive metals (K, Na, Ca, Mg, Al) are extracted by electrolytic reduction of their molten compounds because no chemical reducing agent is strong enough. Medium reactive metals (Zn, Fe, Cu) are first converted to their oxides by roasting (sulphide ores heated in air) or calcination (carbonate ores heated without air), then reduced using carbon (coke). Less reactive metals (Cu, Hg, Ag, Au) can be obtained by simply heating their oxides — they decompose easily. Refining is done by electrolytic refining: impure metal is the anode, pure metal strip is the cathode, and metal salt solution is the electrolyte.

When metals react with non-metals, electrons are transferred from the metal atom to the non-metal atom. The metal atom loses electrons to become a positively charged cation, and the non-metal atom gains electrons to become a negatively charged anion. The electrostatic attraction between these oppositely charged ions forms an ionic bond. Ionic compounds have a regular, ordered crystal structure. Due to the strong electrostatic forces between ions, ionic compounds have high melting and boiling points, are hard but brittle (layers shift and like-charges repel), conduct electricity when molten or dissolved in water (ions are free to move), but do not conduct in solid state (ions are fixed in position).