Chemical element: What is, how is its classification and periodic table

A chemical element is understood as a pure substance composed only by equal or the same type atoms. Unlike mixtures and compounds, the elements cannot decompose in simpler substances through ordinary chemical processes, as stated in basic chemistry texts such as Sánchez, García and Balderas⁽¹⁾. This essential property makes them the fundamental components of the matter. In the periodic table, each element is identified with a specific symbol and is distinguished by its atomic number, which represents the number of protons present in the nucleus and defines its properties.

How many chemical elements are there?

The number of chemical elements has increased progressively. 118 chemical elements are known, of which 90 are natural and the rest synthesized in the laboratory⁽²⁾. The most recent are usually radioactive, with a short half -life and difficult stability.

The classification of the elements is based on their location in the periodic table and its physicochemical properties. In general, they are divided into metals, non -metals and metalloids, while noble and halogen gases form particular groups.

Metals

Metals are the widest family of the periodic table, located to the left of the Zigzag line (except hydrogen). They are distinguished by their brightness, conductivity, malleability and ductility, in addition to forming cations easily. They include alkaline, alkaliners, transition, lanthanides and actinids, with great importance in construction, cables, electronics and catalysis. For example: gold, silver, iron, copper, aluminum and mercury.

No metals

Non metals are found to the right of the periodic table and are characterized by being bad conductors, fragile in solid state and presenting themselves in various physical states. They form anions by gain electrons, have low density and fusion points, generate acid and oxyacid oxides, and are essential for life by integrating organic and inorganic compounds. For example: oxygen, nitrogen, sulfur and carbon.

Metalloids

Metalloids, located in the Zigzag line of the periodic table, have intermediate properties between metals and non -metals. They include Boro, Silicon, Germanio, Arsenic, Antimony, Telurio and Polonio. They are hard, fragile, with semimetallic brightness and intermediate conductivity. They stand out as semiconductors, being the fundamental silicon in integrated circuits and modern electronic devices. For example: silicon, boron and arsenic.

Noble gases

The noble gases, located in group 18, are monoatomic, colorless, diamagnetic and very little reactive for their stable electronic configurations. Generally, they do not form compounds, although some have been synthesized with xenon and crypton. They have relevant applications: neon is used in light ads and helium, light and non -flammable, in hot air balloons. For example: helium, neon, argon, crypton, xenon and radon.

Halogens

The halogens, group 17 of the periodic table, are not very reactive metals whose name means “salts of salts.” They form diatomic and haluros molecules when joining metals. Its reactivity decreases with the increase in atomic mass. They are found as natural salts and apply in disinfection, oxidation, drugs and polymers. For example: fluorine, chlorine, bromine, iodine, and astato.

The periodic table organizes the elements according to their atomic number and electronic structure. Created by Mendeleiev in 1869 from the atomic mass, it allowed to anticipate unknown elements. In its modern version, the elements are arranged in periods (rows) and groups (columns), where they share chemical properties for having the same number of electrons in Valencia.

• PERIODS: The table has seven periods. In long periods (4 and 5) the transition elements are located, while periods 6 and 7 include lantanids and actinids.
• Groups: There are 18 groups or families. Alkaline (1), alkaliner (2), halogens (17) and noble gases (18) stand out. Each period begins with an alkaline metal and ends with a noble gas, showing a non -metallic metallic transition.
• Periodic properties: in each period the atomic radius, electronegativity and ionization energy vary systematically, increasing the non -metallic character.

• Industry and technology: metals such as iron, copper and aluminum are applied in construction, machinery and cables; Chromium is used in chrome and vanadium in more resistant steel alloys.
• Health and daily chemistry: halogens such as chlorine and iodine are essential in disinfection and nutrition; Oxygen and carbon are vital in breathing and biochemistry.
• Advanced technology: metalloids such as silicon and Germanio stand out as semiconductors in circuits, sensors and optical fibers.
• Noble gases: neon illuminates ads and helium is used in globes and cryogenic cooling.
• Energy and Defense: Actinids such as Uranium and Plutonium support nuclear energy and military applications.

The main difference is that the element contains a single type of atom, while the compound integrates atoms other than different chemical elements linked chemically.

A chemical element is a pure substance constituted by atoms of the same type, indivisible in simpler substances by common chemical processes; Examples are iron, oxygen or gold. On the other hand, a chemical compound results from the chemical union of two or more elements in fixed proportions, acquiring properties other than the originals; For example, water and sodium chloride. The compounds have defined chemical formula and are not easily separated by physical methods.

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