The chemical elements are the building blocks of matter. All the substances that surround us are an element or a compound formed by chemical elements.
The chemical element is composed of a single type of atom. Recall that an atom is the smallest particle of an element that retains its properties.
The monatomic elements are those elements formed by an element. For example Fe iron. There are diatomic elements, that is, they are made up of two identical atoms, such as hydrogen 
and oxygen.
118 elements have been discovered of which 98 occur naturally on Earth. Of these, 80 are stable elements and 18 are radioactive.
The elements are arranged in the periodic table in increasing order of atomic number. The atomic number refers to the number of protons that the element atom has.
Characteristics of chemical elements
- They have the same atoms.
- They have the same number of protons.
- The elements combine to form compounds: sodium Na and chlorine Cl combine to form sodium chloride NaCl, or table salt.
- The elements can not be divided into smaller parts without a large amount of energy.
- The chemical behavior of the elements is related to the structure of the nucleus and the configuration of its electrons.
- The elements in the same group of the periodic table present similar chemical behaviors.
- They can be found in different states: solid (such as iron, Fe), gas (helium, He), and liquid (mercury, Hg) at room temperature.
Classification of the elements
Position of metals, metalloids, and non-metals in the periodic table.
The chemical elements are divided into metals, metalloids, and non-metals. Most of them are metals, only 11 elements are not metals, and 8 are metalloids. The non-metals are:
- Hydrogen H,
- carbon C,
- nitrogen N,
- Oxygen,
- phosphorus P,
- sulfur S,
- Selenium Se,
- fluor F,
- chlorine Cl,
- Br brom
- Iodine I.
- boro B,
- silicon Yes,
- Germanium Ge,
- arsenic As,
- bismuth Sb,
- Tellurium, Te,
- polonium Po,
- Astatine, At.
The most abundant elements of the universe are hydrogen and helium. Iron is the most abundant element in the composition of the Earth. Oxygen is the most common element in the earth’s crust.
The symbols of chemical elements
Most elements are represented by their chemical symbol, which is the first or the first two letters of their name. They come to be the abbreviated form of the names of the chemical elements. This greatly facilitates the work of chemists when they are writing compound formulas.
Always the first letter is written with a capital letter. For example: for hydrogen it is H, for oxygen it is O and for calcium, it is Ca. Ne is for neon and Se is selenium.
Some symbols of the elements come from the words of origin (Greek, German or Latin). Mercury is Hg by the Greek hydragyrum which means silver water. Gold is Au for the Latin aurum . An element whose symbol derives from Arabic is potassium or K, from kalium which means alkali.
Important chemical elements for living beings
Of all the chemical elements known in nature, barely a dozen are relevant to the maintenance of life on Earth. Let’s see some of the most important elements for living beings and their function.
Oxygen O
Atomic number 8, atomic weight 16.
Oxygen is the essential element for life. Ozone is the combination of three oxygen atoms that predominates in the upper layer of the atmosphere. The gaseous oxygen of the atmosphere represents 25% of it.
The cells require oxygen to produce the energy necessary to perform all their activities. Oxygen enters the body through the process of breathing.
Atomic number 6, atomic weight 12.
All living beings contain carbon in their composition. It represents about 18% of body mass. Its atomic number is 6 and its valence is 4, which means that it can be combined with 4 different elements.
Carbon is the primordial element in proteins, lipids, nucleic acids, and carbohydrates.
Calcium Ca
Atomic number 20, atomic weight 40.
It belongs to the group of alkaline earth elements. In the body, calcium is found circulating in the blood, in the structure of the bones, and in the muscle. Calcium is important in muscle contraction and in the process of blood coagulation in animals. It is also required for the function of neurons.
We get calcium from milk, yogurt, fish, and green vegetables. Calcium deficiencies produce osteoporosis, a disease where bones are fragile.
Iodo I
Atomic number 53, atomic weight 127.
Iodine belongs to the group of halogens. Its symbol is I. It is important in the synthesis of thyroid hormones, which control metabolism. We get it from marine foods, dairy products, and salt that has been iodized. Its deficiency manifests itself with goiter.
Iron Fe
Atomic number 26, atomic weight 56.
Iron is an important element in the transport of oxygen to cells. Foods like red meat, dried fruits, grains are rich in iron. Deficiency manifests as anemia, which is a decrease in red blood cells or hemoglobin in the blood.
Phosphor P
Atomic number 15, atomic weight 31.
Phosphorus, whose chemical symbol is P, is part of the nucleic acids and molecules that provide energy in the cell. It is found in milk, cheese, meat, and grains. Its deficiency leads to weakness and deformation of the bones.
Zinc
Atomic number 30, atomic weight 65.
The symbol for zinc is Zn. The best sources of zinc are meat, seafood, and poultry. Zn is linked to enzymes and participates in biochemical reactions. It is also part of DNA-binding proteins. Zn deficiencies are rare but manifest as problems in the functions of the immune system.
The name of the elements
There is no fixed rule to name the elements. Some have the name of scientists like Mendelevio Md, of places, like Americio Am (95), Europio Eu, or names of planets Uranio U, Plutonio Pu. And Mercury Hg. Ag derives from the Latin argentum which means silver.
Isotope of a chemical element
Isotopes are different forms of an element that have the same number of protons, but change the number of neutrons. The way to call them is with the name of the element followed by the sum of protons and neutrons. For example, carbon 12 has 6 protons and six neutrons; Carbon 14 has six protons and 8 neutrons.
Differences between compounds and elements
A compound is made of one or more elements in a predetermined proportion. For example, water H 2 O is a compound made of two elements: hydrogen H and oxygen O.
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