We explain what a chemical element is, its characteristics and examples. Also, the periodic table and chemical compounds.
What is a chemical element?
A chemical element is each of the fundamental forms of matter. It is always presented as atoms of the same and unique type and that, therefore, cannot be decomposed into simpler substances using chemical reactions.
When we talk about a chemical element or simply an element, we mean a certain type of known atoms, which are distinguished from the others in their nature and their fundamental properties. This is usually expressed by different symbols for each one.
Chemical elements are atoms. But the following must be understood: the atoms that are part of the same chemical element have the same number of protons in their nucleus (atomic number), although they have different atomic mass.
There are atoms that have the same atomic number, that is, they belong to the same chemical element, but have a different number of neutrons, so their mass number (sum of protons and neutrons) is different. These types of atoms are called isotopes.
In other words, each chemical element has different amounts of the isotopes that make it up.
For instance, the element hydrogen has three natural isotopes: the protium (1H), deuterium (2H) and tritium (3H). Protium is made up of a proton and an electron (it has no neutrons), and it is the most abundant isotope of hydrogen. Deuterium is made up of a proton and a neutron in its nucleus, and an orbiting electron. The nucleus of tritium is made up of 1 proton and two neutrons, and is a radioactive isotope. Other isotopes of the element hydrogen have also been synthesized in laboratories.
When a chemical reaction occurs between two or more substances, it is their chemical elements that are exchanged and combined, forming new atomic bonds and thus forming new forms of matter. Everything that exists is made up of combinations of the same elements.
Chemical elements in the Periodic Table
The Periodic Table of the Elements is an orderly way of representing all known chemical elements (expressed by their chemical symbols). They are grouped based on their electronic and chemical properties, going from those with the lowest atomic number to those with the highest atomic number through their rows and columns.
This table It was presented in its first version by Dmitri Mendeleev in 1869. Since then it has been expanded, updated and improved, to obtain its most current versions.
The Periodic Table distributes the elements in rows (called periods) and in columns (called groups), thus forming sets of elements classified in different categories, such as: metals (divided into alkaline, alkaline earth, lanthanides, actinides, transition metals and other metals), metalloids and nonmetals (divided into halogens, Noble gases and other non-metals).
The IUPAC version of the Periodic Table can be viewed here.
Examples of chemical elements
Some of the best known chemical elements are:
- Hydrogen (H)
- Carbon (C)
- Oxygen (O)
- Nitrogen (N)
- Phosphorus (P)
- Sulfur (S)
- Aluminum (Al)
- Iron (Fe)
- Chlorine (Cl)
- Iodine (I)
- Sodium (Na)
- Calcium (Ca)
- Potassium (K)
- Mercury (Hg)
- Silver (Ag)
- Gold (Au)
- Copper (Cu)
- Uranium (U)
- Argon (Ar)
- Zinc (Zn)
- Helium (He)
- Neon (Ne)
- Lead (Pb)
How many elements are there?
Currently 118 different elements are known, each described in the Periodic Table. However, some of them are synthetic, that is, artificial: they do not exist in nature but only in the laboratories of humanity.
The latest chemical technologies have made it possible to find up to 129 different elements, many of which do not exist beyond a short period of time under very specific conditions of a specialized laboratory.
Chemical compound
Chemical compounds are understood to be the forms of matter that arise from the combination of the different chemical elements. They can be relatively simple compounds such as some binary molecules (for example carbon dioxide (CO2)) or complex compounds with many different atoms, such as organic macromolecules (for example, DNA).
The truth is that all compounds are substances that can decompose, given the appropriate chemical reactions, in their constituent elements, becoming increasingly simple until they reach monatomic or elemental substances. For example, water (H2O) can be decomposed by electrolysis into hydrogen and oxygen molecules, both in the form of gas.