Allotropes, Alloys and Ores of metals and non-metals

Allotropes, Alloys and Ores of metals and non-metals

Both metals and non-metals show polymorphism or allotropy. This is the occurrence of an element in more than one form but in the same physical state. These forms are called polymorphs or allotropes.

Elements                      Major Allotropic Forms

Carbon                          Diamond and Graphite

Sulphur                          Rhombic sulphur

                                        Monoclinic sulphur

Tin                                  White tin and Red tin

Oxygen                           Dioxygen (Oxygen)

                                        Trioxygen (Ozone)

Phosphorus                   White phosphorus

                                         Red phosphorus

All the allotropes of an element have the same chemical properties even though they have different appearances or crystalline strictures. For instance, diamond (a hard form of carbon) and graphite (a soft form of carbon) can be shown to be the same element by combustion whereby a sample of each allotrope is burnt in excess oxygen. The product in each case is carbon(IV)oxide.

Metals are at times mixed intimately with other metals or non-metals to form alloys. The alloys combine the strength and the properties of the constituent elements.

Examples:

Alloys                       Constituent Elements

Brass                            Copper and Zinc

Bronze                          Copper and Tin

Steel                              Iron and Carbon

Duralumin                    Aluminum, Magnesium,

                                      Manganese and Copper

Sodium Amalgam       Sodium and Mercury

Zinc Amalgam              Zinc and Mercury

It should be noted that an amalgam is an alloy of mercury and another metal.

The form in which a metal occurs naturally is known as the ore. Metals can be removed or extracted from their ores by various means depending on their degree of activity. The activity series is the arrangement of elements in the decreasing order of reactivity or electropositivity or metallicity.

Those metals that are highly or moderately reactive do not occur free in nature but rather they occur in form of compounds in their ores.

The compounds found in ores are usually oxides or sulphides or trio of at on area (IV) of metals. These ores are either concentrated (by floatation) or roasting (heating in air) and then reduced chemically or electrolytically to release or free their metals. Elements in this category include potassium, sodium, calcium, aluminium and iron.

Ores                          Element sought

Haemitite                          Iron

Casseterite                       Tin

Bauxite                        Aluminum

Zinc blend                        Zinc

Galena                             Lead

Malachite                      Copper

However, there are other metals that have low reactivity and so they are usually found free in nature. Such metals include Platinum and Gold.

Metalloid are elements that are neither distinctly metallic nor clearly non-metallic e.g. Silicon, Arsenic, Tellurium, etc. The properties of metalloids are intermediate between those of metals and those of non-metals. For instance, they are semiconductors rather than being good conductors or nonconductors of electricity.