Periodic table

periodic table of elementsperiodic table of the elementsperiodic systemperiodic table of the chemical elementsperiodicityelementperiodic system of elementsThe Periodic Tablechemical elementsperiodic law
The periodic table, also known as the periodic table of elements, is a tabular display of the chemical elements, which are arranged by atomic number, electron configuration, and recurring chemical properties.wikipedia
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Halogen

halogensgroup 1717
Six groups have accepted names as well as assigned numbers: for example, group 17 elements are the halogens; and group 18 are the noble gases.
The halogens are a group in the periodic table consisting of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

Periodic trends

periodic lawperiodic trendgroup trends
The structure of the table shows periodic trends.
Periodic trends are specific patterns in the properties of chemical elements that are revealed in the periodic table of elements.

Electron configuration

electronic configurationconfigurationelectronic structure
The periodic table, also known as the periodic table of elements, is a tabular display of the chemical elements, which are arranged by atomic number, electron configuration, and recurring chemical properties. Columns (groups) are determined by the electron configuration of the atom; elements with the same number of electrons in a particular subshell fall into the same columns (e.g. oxygen and selenium are in the same column because they both have four electrons in the outermost p-subshell).
Knowledge of the electron configuration of different atoms is useful in understanding the structure of the periodic table of elements.

Group (periodic table)

groupgroupsChemical series
The columns, called groups, contain elements with similar chemical behaviours. Columns (groups) are determined by the electron configuration of the atom; elements with the same number of electrons in a particular subshell fall into the same columns (e.g. oxygen and selenium are in the same column because they both have four electrons in the outermost p-subshell).
In chemistry, a group (also known as a family ) is a column of elements in the periodic table of the chemical elements.

Hydrogen

HH 2 hydrogen gas
The elements from atomic numbers 1 (hydrogen) through 118 (oganesson) have been discovered or synthesized, completing seven full rows of the periodic table.
With a standard atomic weight of 1.008, hydrogen is the lightest element in the periodic table.

Metal

metalsmetal ionsmetal ion
The seven rows of the table, called periods, generally have metals on the left and non-metals on the right.
Around 95 of the 118 elements in the periodic table are metals (or are likely to be such).

Dmitri Mendeleev

MendeleevDmitri MendeleyevDmitry Mendeleev
Russian chemist Dmitri Mendeleev published the first recognizable periodic table in 1869, developed mainly to illustrate periodic trends of the then-known elements.
He is best remembered for formulating the Periodic Law and creating a farsighted version of the periodic table of elements.

Chemical element

elementelementschemical elements
The periodic table, also known as the periodic table of elements, is a tabular display of the chemical elements, which are arranged by atomic number, electron configuration, and recurring chemical properties.
The properties of the chemical elements are summarized in the periodic table, which organizes the elements by increasing atomic number into rows ("periods") in which the columns ("groups") share recurring ("periodic") physical and chemical properties.

Period (periodic table)

periodperiodsperiod 3
The seven rows of the table, called periods, generally have metals on the left and non-metals on the right. A new row (period) is started when a new electron shell has its first electron.
A period in the periodic table is a row of chemical elements.

Oxygen

OO 2 molecular oxygen
Columns (groups) are determined by the electron configuration of the atom; elements with the same number of electrons in a particular subshell fall into the same columns (e.g. oxygen and selenium are in the same column because they both have four electrons in the outermost p-subshell).
It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds.

Isotope

isotopesisotopicisotopic composition
Most elements have differing numbers of neutrons among different atoms, with these variants being referred to as isotopes.
The term isotope is formed from the Greek roots isos (ἴσος "equal") and topos (τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table.

Atomic orbital

orbitalatomic orbitalselectron cloud
Also displayed are four simple rectangular areas or blocks associated with the filling of different atomic orbitals.
The repeating periodicity of the blocks of 2, 6, 10, and 14 elements within sections of the periodic table arises naturally from the total number of electrons that occupy a complete set of s, p, d and f atomic orbitals, respectively, although for higher values of the quantum number n, particularly when the atom in question bears a positive charge, the energies of certain sub-shells become very similar and so the order in which they are said to be populated by electrons (e.g. Cr = [Ar]4s 1 3d 5 and Cr 2+ = [Ar]3d 4 ) can only be rationalized somewhat arbitrarily.

Oganesson

Og118Ghiorsium
The elements from atomic numbers 1 (hydrogen) through 118 (oganesson) have been discovered or synthesized, completing seven full rows of the periodic table.
On the periodic table of the elements it is a p-block element and the last one of period 7.

Selenium

SeSe 3 selenium poisoning
Columns (groups) are determined by the electron configuration of the atom; elements with the same number of electrons in a particular subshell fall into the same columns (e.g. oxygen and selenium are in the same column because they both have four electrons in the outermost p-subshell).
It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic.

Group 4 element

group 44Group 4 elements
The roman numerals used correspond to the last digit of today's naming convention (e.g. the group 4 elements were group IVB, and the group 14 elements were group IVA).
Group 4 is a group of elements in the periodic table.

Group 3 element

group 33III
Groups 3–10 have no trivial names and are referred to simply by their group numbers or by the name of the first member of their group (such as "the scandium group" for group 3), since they display fewer similarities and/or vertical trends.
Group 3 is a group of elements in the periodic table.

Atomic number

proton numberZatomic numbers
The periodic table, also known as the periodic table of elements, is a tabular display of the chemical elements, which are arranged by atomic number, electron configuration, and recurring chemical properties.
The conventional symbol Z comes from the German word Zahl meaning number, which, before the modern synthesis of ideas from chemistry and physics, merely denoted an element's numerical place in the periodic table, whose order is approximately, but not completely, consistent with the order of the elements by atomic weights.

Chemistry

chemistchemicalApplied Chemistry
The modern periodic table now provides a useful framework for analyzing chemical reactions, and continues to be widely used in chemistry, nuclear physics and other sciences.
The standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number.

Group 11 element

group 1111coinage metals
There are exceptions to these trends: for example, in group 11, electronegativity increases farther down the group.
Group 11, by modern IUPAC numbering, is a group of chemical elements in the periodic table, consisting of copper (Cu), silver (Ag), and gold (Au).

Block (periodic table)

d-blockp-blockf-block
Also displayed are four simple rectangular areas or blocks associated with the filling of different atomic orbitals.
A block of the periodic table is a set of chemical elements having their differentiating electrons predominately in the same type of atomic orbital.

International Union of Pure and Applied Chemistry

IUPACInternational Union of Pure and Applied Chemistry (IUPAC)International Congress of Applied Chemistry
Elements 113, 115, 117 and 118, the most recent discoveries, were officially confirmed by the International Union of Pure and Applied Chemistry (IUPAC) in December 2015.

Electron shell

valence shellshellshells
A new row (period) is started when a new electron shell has its first electron.
The first elements to have more than 32 electrons in one shell would belong to the g-block of period 8 of the periodic table.

Group 10 element

group 101010 (Ni, Pd, Pt…)
In Europe, the lettering was similar, except that "A" was used if the group was before group 10, and "B" was used for groups including and after group 10.
Group 10, numbered by current IUPAC style, is the group of chemical elements in the periodic table that consists of nickel (Ni), palladium (Pd), platinum (Pt), and perhaps also the chemically uncharacterized darmstadtium (Ds).

Atomic radius

atomic radiiatomicatomic size
Elements in the same group tend to show patterns in atomic radius, ionization energy, and electronegativity.
Atomic radii vary in a predictable and explicable manner across the periodic table.

Proton

protonsH + p
In the standard periodic table, the elements are listed in order of increasing atomic number Z (the number of protons in the nucleus of an atom).
Following the discovery of the atomic nucleus by Ernest Rutherford in 1911, Antonius van den Broek proposed that the place of each element in the periodic table (its atomic number) is equal to its nuclear charge.