What is a chemical element?
A chemical element is each of the fundamental forms of matter. It always occurs as atoms of the same and unique type and, therefore, cannot be broken down into simpler substances using chemical reactions.
When we speak of a chemical element or simply of an element, we refer to 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.
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), even though they have different atomic masses.
Some atoms 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 compose it.
For example, the element hydrogen has three naturally occurring isotopes: protium (1H), deuterium (2H), and tritium (3H). Protium is made up of one proton and one 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 electron orbiting it. 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, constituting 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 a way of representing all the known chemical elements (expressed using their chemical symbols) in order. They are grouped based on their electronic and chemical properties, ranging from those with the lowest atomic number to those with the highest atomic number through their rows and columns.
This table was presented in its first version by Dmitri Mendeleev in 1869. Since then it has been expanded, updated, and improved, until obtaining 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 into 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 nonmetals ).
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 one 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 under very specific conditions in a specialized laboratory.
Chemical compounds are understood as the forms of matter that arise from the combination of different chemical elements. They can be relatively simple compounds such as some binary molecules (eg carbon dioxide (CO2)) or complex compounds with many different atoms, such as organic macromolecules (eg DNA).
The truth is that all compounds are substances that can be broken down, given the appropriate chemical reactions, into their constituent elements, becoming increasingly simple until they reach monatomic or elemental substances. For example, water (H2O) can be broken down by electrolysis into hydrogen and oxygen molecules, both in gas form.