We explain what metalloids are and what their shapes and color are like. Also, what are its characteristics, properties and uses.
What are metalloids?
Metalloids or semimetals are a type of chemical elements that show intermediate behavior between metals and non-metalsin terms of ionization energies and binding properties.
It is not easy to distinguish them from true metals. They conduct electrical current better than non-metals, but are not good conductors like metals. Besides, They are usually very varied in their shape and coloration.
The list of metalloids includes the following elements:
- Boron (B)
- Silicon (Yes)
- Germanium (Ge)
- Arsenic (As)
- Antimony (Sb)
- Tellurium (Te)
- Polonium (Po)
See also: Alkali metals
Characteristics of metalloids
- Location on the Periodic Table. The metalloids are found in the Periodic Table in a descending diagonal from boron to polonium, spread across columns 13, 14, 15 and 16, dividing the table in two. The elements located in the middle on the right are non-metallic, and those located on the left are metallic.
- Shape and coloration. Metalloids are very varied in terms of shape and color. They can be shiny or opaque, and many of them present more than one allotropic state, that is, different presentations according to their molecular structure. Arsenic, for example, can be gray, yellow or black, depending on its allotropic form. Silicon, similarly, can appear as a shiny solid crystal or as an amorphous, brownish powder.
- Electric driving. Most metalloids are semiconductors (they can behave as conductors or insulators, and transmit electricity better in one direction than the other) rather than complete conductors and in this they are distinguished from metallic elements. However, they are much better conductors than non-metal elements (insulators), which is why they are often used in the electronic manufacturing industry.
- Thermal conduction. Metalloids conduct heat energy much better than non-metallic elements, without reaching the high conductivity of metallic elements. In general terms, they are not considered good conductors of heat.
- Reactivity. Given their intermediate condition, metalloids react differently depending on whether they are in the presence of a metallic element (then they react like a non-metal) or a non-metallic element (then they react like a metal). They have an affinity for various elements, depending on each one, and that is why they are usually found in minerals along with them, such as uranium, lead, sulfur, etc.
- Toxicity. Although some metalloids are essential for the formation of vital molecules (for example arsenic, which is found in the body of living beings), they may represent a danger to health. Poisoning by boron or arsenic itself (highly toxic) can be lethal; and polonium is a toxic and highly radioactive element, that is, it emits alpha particles that are harmful to health, as they are potentially carcinogenic, immunosuppressive and mutagenic.
States of aggregation of metalloids
Most metalloids usually appears in solid state at room temperatureeither in the form of crystals (such as arsenic) or opaque and brittle blocks (such as germanium).
However, some have curious properties regarding the change of phases. For example, arsenic goes directly from solid to gas (sublimation) in the presence of heat (and at normal atmospheric pressures).
Atomic properties of metalloids
Metalloids are very diverse in their atomic characterization. There are some with great atomic weight such as polonium (209 u) or antimony (121.76 u), and others that are rather light such as boron (10.81 u) and silicon (28.08 u).
The same happens with their densities, which range from 2.37 g/cm3 (boron) to 9.32 g/cm3 (polonium) and with its electronic configuration, which can have a different number of electrons in the last layer: 3 (boron), 4 (silicon, germanium), 5 (arsenic, antimony) and 6 (tellurium, polonium).
Abundance of metalloids
Some metalloids They are extremely abundant in the Earth’s crustsuch as silicon, which forms numerous compounds called silicates, or arsenic.
Boron, on the other hand, exists abundantly, but as part of the mineral called borax, since it does not exist in a free and pure state in nature.
Polonium, on the other hand, is quite rare and appears only as part of certain uranium minerals; and antimony is found in very small percentages in the Earth’s crust.
Uses of metalloids
Most semimetals They are used for the manufacture of electronic devices and semiconductor elements, such as rectifiers, transistors, diodes, integrated circuits or even (as in the case of silicon), chips and microprocessors. However, their variety equips them for numerous different uses.
For example, Some boron isotopes are useful in absorbing neutrons within nuclear power plants, and function as mechanisms for regulating atomic reactions.
Continue with: Noble gases
References:
- Trace Elements in Human and Animal Nutrition. 5th edition. Walter Mertz. 1986. ISBN: 9780124912526
- Main chemical compounds. Claramunt Vallespí Rosa M, Conargo Ramírez Pilar, Esteban Santos Soledad, Farrán Morales Angeles, Pérez Torralba Marta and Sanz del Castillo Dionisia. 2015. ISBN:978-84-362-6916-1
- “Semimetal” on Wikipedia.
- “Metaloid” in Quimica.es.