Metal

Metal is a class of materials typically characterized by high electrical and thermal conductivity, malleability, ductility, and a lustrous appearance when polished.  These properties arise from their unique atomic structure, specifically the presence of delocalized electrons that are not bound to individual atoms but are free to move throughout the material.  This metallic bonding is responsible for their ability to conduct electricity and heat so efficiently, as well as their capacity to be shaped without breaking.  While most metals are solid at room temperature (with mercury being a notable exception), their specific properties can vary widely depending on the element or alloy, leading to diverse applications across countless industries, from construction and electronics to jewelry and medicine.

Metals are one of the major categories of engineering and structural materials and include both pure elements, such as iron, copper, aluminum, gold, and titanium, and alloys, which are mixtures of two or more elements designed to achieve specific properties.  Because of their strength, toughness, durability, and ability to conduct heat and electricity, metals are widely used in construction, transportation, manufacturing, electrical systems, machinery, and countless industrial applications.

From a scientific perspective, metals occupy the left and center regions of the periodic table and generally tend to lose electrons during chemical reactions, forming positive ions.  Their combination of mechanical strength, formability, and conductivity has made them among the most important materials in human civilization, from ancient tools and structures to modern aerospace, energy, and electronic technologies.

Metals Types

Ferrous Metals  -  These contain iron as a primary component and include iron itself, carbon steels, alloy steels, stainless steels, cast iron, and wrought iron. They are generally magnetic and prone to rusting unless protected.
Non-ferrous Metals  -  These do not contain significant amounts of iron and include aluminum, copper, zinc, lead, tin, nickel, titanium, magnesium, and precious metals such as gold and silver. They are typically non-magnetic and often more resistant to corrosion.
Alkali Metals  -  Found in Group 1 of the Periodic Table and they are highly reactive and usually found with other elements in nature, rarely by themselves.  These are silvery colored, soft, low density metals.
Alkaline Earth Metals  -  The alkaline earth metals are a group of chemical elements found in Group 2 of the periodic table. These elements are silver colored, soft metals that will only melt at very high temperatures.
Transition Metals  -  A group of elements found in the central portion of the periodic table, spanning from groups 3 to 12.  These elements are known for their unique electronic configurations, particularly the filling of their d orbitals.
Post-transition Metals  -  Elements found in the periodic table between the transition metals and the metalloids.  They include elements from groups 13 to 16 (boron to radon).
Inner transition metals   -  Comprising the lanthanides (rare earth elements) and actinides, located in the two bottom rows of the periodic table.

Additional established categories include heavy metals (high density, such as lead and mercury), light metals (low density, such as aluminum and magnesium), refractory metals (high melting points, such as tungsten and molybdenum), noble metals (highly resistant to corrosion, such as gold and platinum), and base metals (common metals that oxidize easily).  Metals can also exist as pure elements or as alloys (mixtures like steel or bronze).

Physical Forms  -  Most metals are naturally solid at room temperature, except for mercury, which is liquid at room temperature.  In physical form, metals can be defined as substances, which have a bright luster and are good conductors of heat and electricity.  They have varying degrees of density, hardness, malleability and ductility.

Form Alloys  -  Metals can be mixed with other elements to form alloys, which are materials with improved properties (such as increased strength or corrosion resistance).

Heat Resistance  -  Metals have high melting and boiling points, allowing them to remain solid in high temperatures. 

Conductivity  -  Metals are known for their ability to conduct electricity and heat due to free electrons that move freely throughout the metal and carry electrical and thermal current.

Density -  Metals are dense, solid materials that weigh more than nonmetals.  Density is characteristic of the material from which the object is made, and its value can help identify the material.

Malleability and Ductility  -  Metals are malleable and ductile, allowing them to be pounded, rolled into different shapes, or drawn into wire without breaking.

Color  -  The color of metal can vary depending on factors such as the specific type of metal, its surface treatment, and the presence of impurities or alloying elements.  In its pure form, many metals have a characteristic metallic luster, which gives them a shiny, reflective appearance.  This luster arises from the metal’s ability to reflect light.  However, pure metals can also exhibit different colors.

Luster  -  A physical property that describes how a mineral's surface and structure interact with light.  Luster describes how a mineral reflects and refracts light.

Ionization  -  Metals are prone to losing electrons and forming positive ions.  This is because the outermost electrons in a metal’s atoms are not strongly attracted to the positively charged nucleus and can be easily removed.

Electropositivity  - The capability of an atom to donate electrons and generate positively charged cations is known as electropositivity.  Metallic elements, particularly alkali metals and alkaline earth metals, are known to have this feature.  Electropositivity is the reverse of electronegativity, which is a measurement of an atom’s tendency to acquire electrons and create negatively charged anions.  As a result, electropositive elements have very low electronegativities, whereas highly electronegative elements have low electropositivity.

Reactivity  -  React with oxygen to form metal oxides (rust in iron).  Reactive metals lose electrons easily and produce vigorous (explosive or potentially dangerous) reactions with water or acids.  Unreactive metals do not lose electrons easily and are inert under normal conditions and with substances they are likely to encounter.

Corrosion  -  Some metals react with air and water, leading to corrosion.  Corrosion can have either positive or negative effects, but we wouldn’t advise picking a metal that isn’t corrosion resistant when you need it to be.  But you have to consider the instability and potential damage corrosion can cause.

Alloy Formation  -  Metals can combine with other metals or elements to form alloys.  Because alloys combine different elements, they contain atoms of different sizes.  How these atoms combine and interact with one another gives alloys their classification.  In alloy chemistry, an alloy can be classified as substitutional or interstitial, according to its atomic arrangement.

The physical properties of metals have characteristic such as shiny, hard, high density, malleable, high melting point and can conduct electricity and heat well.  Metals are essential in various industries, from construction and transportation to electronics and healthcare.