We explain what chemical elements are, how they originated and their classification. Also, what are its characteristics and some examples.
What are chemical elements?
A chemical element is called matter that is composed of the same type of atom, that is, it is atomically pure. They are substances that cannot be decomposed into simpler substances through chemical reactions and that are classified in the periodic table of chemical elements.
Elements should not be confused with simple substances., since in certain cases two or more atoms of the same type can be grouped differently. For example, two simple substances can be composed from oxygen atoms (O): ozone (O3) and molecular oxygen (O2).
Most of the known elements come from naturewhere they can be found in monatomic form or forming compounds with other elements. Some even exist in artificial form, due to man’s inventiveness.
Depending on the element, it will have certain properties and, therefore, different uses and applications.
Nor should the chemical elements be confused with the “four elements” (water, fire, air, earth), which respond to an ancient classification of the forces involved in nature.
See also: Separation of mixtures
Origin of chemical elements
The chemical elements They are formed, as far as we know, inside stars.as a product of complex processes of atomic fusion and fission that generate increasingly heavier elements in a process called nucleosynthesis.
We assume that This is how all the matter in the universe would have originatedexcept that which human beings have been able to create on their own in our laboratories and nuclear reactors.
Nomenclature and representation of chemical elements
Chemical elements are usually baptized with names from the Greco-Roman mythological traditionas is the case with mercury, since many of the theories about the origin and essence of the universe that we have been dealing with for centuries come from these cultures.
In other cases, however, a name derived from the surname of its discoverer is usually givenas is the case with lawrencium, named after the team of physicists at Lawrence Berkeley National Laboratory who first synthesized it.
The chemical elements They are represented by one or a combination of letters (acronyms)which summarizes the entire name of the atom, for example: oxygen (O), mercury (Hg) and lawrencium (Lr).
Abundance of chemical elements
There are currently 118 known chemical elementsbetween natural and artificial ones. The former tend to be found in a pure state (like atmospheric helium) or forming chemical compounds (like iron, rarely in a pure state). This will depend on the reactivity of the element and its characteristic affinities.
Artificial elements are generally rather unstable. and often release dangerous amounts of energy and matter (radioactivity). This decay process can last fractions of a second, as in the case of oganesson (Og), or it can take hundreds or even millions of years, as in the case of plutonium (Pu).
Periodic table
The periodic table It was created by Dmitri Mendeleev in 1869to visually order the known chemical elements based on their properties and characteristics.
Today, after numerous updates and modifications, we use a new version which includes the recently synthesized elements and which serves as a tool for the atomic study of nature.
Classification of chemical elements
Chemical elements can be classified based on their properties, as distinguished and organized by the periodic table. In this sense, we speak of:
- Metals. They are solid elements at room temperature (except mercury), dense and very good conductors of heat and electricity. They are generally shiny, that is, they reflect light. They are further classified into actinides, lanthanides, transition metals, alkali metals, alkaline earth metals and other metals.
- No metals. They are elements that are not good conductors of heat or electricity and are too weak to be rolled or stretched as metals are. They are mostly essential for biological systems (organic compounds).
- MetalloidsThey are elements that correspond to an intermediate classification between metals and non-metals, and that combine characteristics of both groups. They are known as semimetals.
- Halogens. It is a group of six elements that tend to form very chemically active diatomic molecules, due to their electronegativity: they usually form mononegative ions (electrically charged molecules). Halogens are highly oxidizing, so these elements tend to be caustic and corrosive.
- Noble gases. It is a group of seven elements whose natural state is gaseous. They generally exist in their monatomic form of very low reactivity and for this reason they are also known as inert gases. They share most of their physical properties and are extremely stable.
Atomic number
The atomic number is a number represented by the letter Z which indicates the number of protons found in the nucleus of the atoms of an element. In the Periodic Table it is usually presented in the upper left part of the box for each element.
This information is very important in chemistry and quantum physics: remember that Protons have a positive charge and electrons have a negative charge.so the atomic number serves to understand (along with the number of electrons) the electromagnetic behavior of atoms.
Atomic mass
The mass of an atom is the equivalent to the sum of the number of particles that has its nucleus: protons and neutrons.
Since a chemical element has several isotopes (atoms of the same chemical element that have different numbers of neutrons) with different atomic masses, the atomic mass of an element is usually calculated as the average of all its known isotopes.
However, it is now known that this procedure is not entirely correct because if the element has one of its isotopes in the vast majority, the mass calculated as an average would refer mainly to the mass of the majority isotope. The strict way to calculate the mass of an atom is to calculate the mass of the isotope of interest and not averaging the mass of all the isotopes.
Valencia
Valencia is the number of electrons that an atom of an element can give up or accept to complete its outermost orbit (last energy level).
Based on this, the atom will be able to form covalent, ionic or metallic bonds, sharing or transferring these electrons with another atom. Some atoms possess more than one valence, so this concept is often preferred to call the “oxidation number.”
Isotopes
Atoms of the same element can vary among themselves, according to their nuclear and energetic properties. Called isotopes to Atoms of the same chemical element that behave differently as far as its core is concerned. Isotopes are different atoms of the same chemical element but that have the same number of protons and a different number of neutrons in their nucleus.
For example, Plutonium is a radioactive element, whose isotope plutonium-238 ends up becoming lead-206; but its longest-lived isotope is plutonium-244, with a half-life (the time it takes for a nucleus to disintegrate) of 80 million years. In contrast, plutonium-239 lasts about 24,100 years, and plutonium-238 lasts just 88 years.
Examples of chemical elements
The best known chemical elements are:
It may be useful to you: Organic compounds
References:
- “The periodic table of elements” in WebElements.
- Periodic law and periodic system of elements by Mendeleev. NP Agafoshin. 1977. ISBN: 978-84-291-7021-4
- Nature’s building blocks: an A-Z guide to the elements. Emsley, John. 2003. ISBN: 0198503407
- “Chemical element” in Wikipedia.