Metal properties Chemical properties The largest part metals in metal identification are chemically reactive, reacting with oxygen in the air to form oxides over shifting timescales (for illustration iron rusts over years and potassium burns in seconds). The alkali metals react quickest followed by the alkaline earth metals, found in the leftmost two groups of the periodic table. The transition metals take much longer to oxidize (such as iron, copper, zinc, nickel). Others, like palladium, platinum and gold, do not respond with the atmosphere at all. Some metals form a wall layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny look and good conductivity for many decades (like aluminum, some steels, and titanium). The oxides of metals are basic (as opposed to those of nonmetals, which are acidic), although this may be considered a rule of thumb, rather than a fact. Painting or anodizing metals are good ways to prevent their corrosion. On the other hand, a more reactive metal in the electrochemical series must be chosen for coating, especially when chipping of the coating is anticipated. Water and the two metals form an electrochemical cell, and if the coating is less reactive than the outer surface, the coating actually promotes corrosion.

Physical properties By tradition, in metal identification have sure characteristic physical properties: they are by and large shiny (they have “luster”), have a high density, are ductile and malleable, usually have a high melting point, are usually hard, and accomplish electricity and heat well. However this is for the most part because the low density, soft, low melting point metals happen to be reactive, and we rarely encounter them in their elemental, metallic form. Metals carry out sound well, that is, they are loud. The electrical and thermal conductivity of metals start off from the fact that in the metallic bond the outer electrons of the metal atoms form a gas of nearly free electrons, moving as an electron gas in a background of positive charge formed by the ion cores. Good mathematical predictions for electrical conductivity, as well as the electrons’ contribution to the heat capacity and heat conductivity of metals can be planned from the free electron model, which does not take the thorough structure of the ion lattice into account.

Whenever considering the exact band structure and fastening energy of a metal, it is necessary to take into account the positive potential caused by the specific arrangement of the ion cores - which is periodic in crystals. The most important consequence of the periodic potential is the formation of a small band gap at the boundary of the brillouin zone. Mathematically, the potential of the ion cores is treated in the nearly-free electron model. As an example an alloy is a combination of two or more elements in solid solution in which the major component is a metal. In metal identification a large amount pure metals are either too soft, brittle or chemically reactive for practical use. Combining different ratios of metals as alloys modify the properties of pure metals to produce pleasing characteristics. The aim of making alloys is generally to make them less brittle, harder, resistant to corrosion, or have a more desirable color and shine. Examples of alloys are steel (iron and carbon), brass (copper and zinc), bronze (copper and tin), and duralumin (aluminium and copper). Alloys specially designed for highly demanding applications, such as jet engines, may contain more than ten elements.