We explain what chemical elements are, how they originated and their classification. Also, what are its characteristics and some examples.
What are the chemical elements?
Chemical element is referred to the material that is composed of one type of atom , i.e., that is atomically pure. They are substances that cannot be decomposed into simpler ones 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, from atoms of oxygen (O) may be composed two simple substances: ozone (O 3 ) and molecular oxygen (O 2 ).
Most of the known elements come from nature , where they can be found monatomically or by forming compounds with other elements. Some even exist in artificial form, due to the inventiveness of man.
Depending on the element it is, it will have certain properties and, therefore, different uses and applications.
Neither 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.
Origin of the chemical elements
Chemical elements are formed, as far as we know, inside stars , as a product of complex fusion and atomic fission processes that generate increasingly heavier elements in a process called nucleosynthesis .
We assume that this is how all the matter in the universe would have originated , except that which humans have been able to create on our 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 tradition , such as mercury , since many of the theories about the origin and essence of the universe that we have handled for centuries come from these cultures .
In other cases, however, a name derived from the surname of its discoverer is usually given , as in the case of Lawrence, named in honor of the team of physicists at Lawrence Berkeley National Laboratory that first synthesized it.
Chemical elements 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 lawrencio (Lr).
Abundance of chemical elements
There are currently 118 known chemical elements , between natural and artificial. The former tend to be in the pure state (like atmospheric helium) or in chemical compounds (like iron , rarely in the pure state). This will depend on the reactivity of the element and its characteristic affinities.
Artificial elements are generally rather unstable and often release amounts of energy and matter (radioactivity) that are dangerous to health. This decomposition process can take fractions of a second, as in the case of oganeson (Og), or it can take hundreds and even millions of years, as in the case of plutonium (Pu).
The periodic table of the elements was created by Dmitri Mendeleev in 1869 , to visually order the known chemical elements based on their properties and characteristics.
Today, after numerous updates and modifications, we are using a new version containing the recently synthesized elements and serving 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 that sense, we talk about:
- Metals . They are solid elementsat room temperature (except mercury), dense and very good conductors of heat and electricity. They are generally bright, that is, they reflect light . They are classified in turn into actinides, lanthanides, transition metals, alkalines , alkaline-earths and other metals.
- No metals . They are elements that are not good conductors of heat or electricity and are too weak to be laminated or stretched as occurs with metals. For the most part, they are essential for biological systems (organic compounds).
- Metalloids . They are elements that correspond to an intermediate classification between metals and non-metals, and that meet the characteristics of both groups. They are known as semimetals.
- Halogens . It is a group of six elements that tend to formchemically very active diatomic molecules , due to their electronegativity: they usually form mononegative ions (electrically charged molecules). Halogens are highly oxidizing, so these elements are often caustic and corrosive.
- Noble gases . It is a group of seven elements whose natural state is gas . They exist, generally, in their monatomic form of very low reactivity and for this reason they are also known as inert gases. They share most of its physical properties and are extremely stable.
The atomic number is a number represented by the letter Z that 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 (together with the number of electrons) the electromagnetic behavior of atoms.
The mass of an atom is equivalent to the sum of the number of particles in 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 mass, the atomic mass of an element is usually calculated as the average of all its known isotopes.
However, today it is known that this procedure is not entirely correct because if the element has one of its isotopes in a large majority, the mass calculated as an average would mainly refer 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 by averaging the mass of all the isotopes.
Valence 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 can form covalent , ionic or metallic bonds, sharing or transferring these electrons with another atom. Some atoms possess more than one valence, which is why this concept is often preferred to call the "oxidation number."
The atoms of the same element can vary among themselves, according to their nuclear and energetic properties. They are called isotopes to the atoms of an element chemical behave differently in regards to its core. Isotopes are different atoms of the same chemical element but that have the same number of protons and 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 (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 only 88 years.
Examples of chemical elements
The best known chemical elements are:
- Oxygen (O)
- Carbon (C)
- Hydrogen (H)
- Nitrogen (N)
- Sulfur (S)
- Iron (Fe)
- Copper (Cu)
- Gold (Au)
- Silver (Ag)
- Mercury (Hg)
- Zinc (Zn)
- Helium (He)
- Phosphorus (P)
- Silicon (Si)
- Sodium (Na)
- Lithium (li)
- Calcium (Ca)
- Platinum (Pt)
- Nickel (Ni)
- Chlorine (Cl)
- Argon (Ar)
- Uranium (U)
- Fluorine (F)
- Potassium (K)
- Neon (Ne)
- Arsenic (As)
- Chromium (Cr)
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