Periodic Table

What is the Periodic Table of the Elements?

The periodic table, or periodic table of the elements, is a organized record of chemical elements according to its atomic number, properties and characteristics.

It is composed of 118 elements confirmed by the International Union of Pure and Applied Chemistry (IUPAC), of which

  • 94 are elements that exist in nature, and
  • 24 elements are synthetic, that is, they have been created artificially.

Its development is closely linked to the discovery of new elements and the study of their common properties. Aspects such as the notion of atomic mass and the relationships between atomic mass and the periodic properties of the elements have been fundamental in shaping the modern periodic table.

The periodic table works as a fundamental tool for the study of chemistry, since it allows the differences and similarities between chemical elements to be consistently and easily identified.

Its creation is attributed to the Russian scientist Dimitri Mendeleev in 1869. Since then, the periodic table has been improved and updated by other scientists as new elements are discovered and studied.

Periodic table

How is the periodic table organized?

The periodic table presents all the elements known so far, which are organized and located according to their characteristics and relationship between them in groups, periods, blocks and metals, metalloids and non-metals.

groups

Periodic table.Group

The periodic table is made up of 18 groups of elements arranged in vertical columns, numbered 1 to 18 from left to right, beginning with the alkali metals and ending with the noble gases.

The elements that belong to the same column have similar chemical characteristics, based on how the electrons in the last layer of the atom are structured.

For example, the first column lists the elements that have an electron in the last shell of the atom. In this case, potassium has four shells and the last one has one electron.

The chemical elements are organized into groups as follows:

  • Group 1 (IA): alkali metals.
  • Group 2 (II A): alkaline earth metals.
  • Group 3 (III B): scandium family.
  • Group 4 (IV B): titanium family.
  • Group 5 (VB): vanadium family.
  • Group 6 (VI B): Chromium family.
  • Group 7 (VII B): manganese family.
  • Group 8 (VIII B): iron family.
  • Group 9 (VIII B): cobalt family.
  • Group 10 (VIII B): nickel family.
  • Group 11 (IB): copper family.
  • Group 12 (II B): zinc family.
  • Group 13 (III A): earthy.
  • Group 14 (IV A): carbonoids.
  • Group 15 (VA): nitrogenoids.
  • Group 16 (VI A): chalcogens or anphigens.
  • Group 17 (VII A): halogens.
  • Group 18 (VIII A): noble gases.
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periods

Periodic table.Periods

Periods are the seven horizontal rows in the periodic table. In these rows are grouped the elements that have the number of electron shells that coincides with the number of the period.

For example, in the first row hydrogen and helium have an electron shell. In period two there are eight elements that have two electron shells. In the third row the elements have three electron shells, and so on.

Elements with six electron shells are found in period six, as are the bottom row of the lanthanides. In period seven are the elements that have seven electron shells, like the last row of the actinides.

Metals, metalloids and non-metals

Three categories of the elements that make up the periodic table can be differentiated based on their chemical and physical properties: metals, metalloids and non-metals.

  • Metals: They are solid elements at room temperature, except for mercury, which is in a liquid state. They are malleable and ductile, and are good conductors of heat and electricity. They are located on the left side of the table.
  • No metals: Most of them are gases, although there are also liquids. These elements are not good conductors of electricity. They are located on the right side of the table.
  • Metalloids or semimetals: They have properties of both metals and nonmetals. They can be shiny, opaque and not very ductile. Its electrical conductivity is lower than metals, but higher than non-metals. They are found on the right side of the table, between metals and non-metals.

blocks

Periodic table.Blocks

The periodic table can also be divided into four blocks based on the sequence of electron shells for each element. The name of each block derives according to the orbital in which the last electron is located.

  • Block s: groups 1 and 2 of the alkali metals, alkaline earth metals, hydrogen and helium.
  • Block p: covers groups 13 to 18 and metalloids.
  • Block d: composed of groups 3 to 12 and transition metals.
  • Block f: does not have a group number and corresponds to the lanthanides and actinides. They are usually placed below the periodic table.
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Periodic table.TrendsPeriodic tendencies refer to the main physical and chemical properties that elements possess and that allow their organization in the periodic table. These trends are related to the changes that occur in the atomic structure of each element according to the period or group to which it belongs.

Among the periodic trends are:

  • Atomic radio: is the distance between the nucleus of the atom and its outermost orbital, which allows us to calculate the size of the atom. It increases from right to left in periods, as well as from top to bottom in groups.
  • Electronic affinity: is described as the energy released by an atom when an electron is added to it or vice versa. It increases in periods from left to right, and in groups it increases upwards.
  • Valence Electrons: refers to the electrons found in the outermost shell of the atom. They increase as the elements are placed from left to right, and are established from the group of the periodic table to which the element belongs.
  • Ionization energy: energy required to remove an electron from an atom. In a period this energy increases to the right, and in a group it increases upwards.
  • Electronegativity: the ability of an atom to attract electrons to itself. It increases from left to right across a period.
  • No metals: the properties of nonmetals increase as the elements are at the top right of the table.
  • Metals: the properties of metals are greater as the elements are located in the lower left part of the table.

Basic data of chemical elements

Periodic tables usually contain fundamental data of each of the elements that exist in it, which allows establishing a coherent organization based on its characteristics such as symbol, name, atomic number and atomic mass, to determine its use.

Periodic table.  Fe(iron)

  • Atomic mass: refers to the mass of the atom, made up of protons and neutrons.
  • Ionization energy: is the energy needed to remove an electron from the atom.
  • Chemical Symbol: abbreviations to identify the chemical element.
  • Name: The name given to the chemical element can be derived from Latin, English, French, German or Russian.
  • Electronic configuration: way in which electrons are structured or organized in an atom.
  • Atomic number: refers to the total number of protons an atom has.
  • Electronegativity: It is the ability of an atom to attract electrons to itself.
  • Oxidation states: indicator of the degree of oxidation of an atom that is part of a compound chemical element.
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What is the periodic table for?

The periodic table is very useful for science studies given the different functions it has.

  • It allows to identify the differences and similarities between the different elements. For example, it contains valuable information such as the atomic mass of each element.
  • It makes it possible to analyze the chemical behavior of elements. For example, by distinguishing the electronegativity and electron configuration of the element.
  • It serves as a fundamental tool for the study of chemistry, including biology and other branches of science, since it identifies the main characteristics of chemical elements.
  • It makes it easy to distinguish elements from their atomic number. This is because elements are made up of atoms, which are named and differentiated by the number of protons, electrons, and neutrons they contain.
  • It can be used to predict the chemical properties of new elements to be included in the table, taking into account the characteristics of the elements already defined.

history of the periodic table

The creation of the periodic table is attributed to the Russian scientist Dmitri Mendeleev, who in 1869 brought together in a table the 63 elements known to science until now.

Mendeleev arranged the elements in increasing order of their atomic masses, taking care to place those with similar physical properties in the same column. He even left empty spaces anticipating the existence of other elements not yet discovered at that time, and which should be included in the table.

Shortly after, the German chemist Julius Lothar Meyer ordered the elements based on the physical properties of atoms. Finally, we owe its current structure to the Swiss scientist Alfred Werner.

The last major changes to the periodic table are the work of Nobel laureate in chemistry Glenn Seaborg, who, among other things, ordered the actinide series below the lanthanide series.

See also:

  • Chemical element.
  • Chemical symbol.
  • Atom