A block of the periodic table

Periodic table

The periodic table of the chemical elements is a tabular display of the 118 known chemical elements organized by selected properties of their atomic structures. Elements are presented by increasing atomic number, the number of protons in an atom's atomic nucleus...

 of elements is a set of adjacent groups

Periodic table group

In chemistry, a group is a vertical column in the periodic table of the chemical elements. There are 18 groups in the standard periodic table, including the d-block elements, but excluding the f-block elements....

. The term appears to have been first used (in French) by Charles Janet

Charles Janet

Charles Janet was a French engineer, company director, inventor and biologist.-Life and work:Janet graduated from the Ecole des Mines and worked for some years in munitions. He then married the daughter of the owner of a manufacturing company and worked for it for the rest of his life, finding...

. The respective highest-energy electrons in each element in a block belong to the same atomic orbital

Atomic orbital

An atomic orbital is a mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus...

 type. Each block is named after its characteristic orbital; thus, the blocks are:

• s-block
  S-block
  The s-block of the periodic table of elements consists of the first two groups: the alkali metals and alkaline earth metals, plus hydrogen and helium.Except in hydrogen and helium, these electrons are very easily lost to form positive ions...
  
  
• p-block
  P-block
  The p-block of the periodic table of the elements consists of the last six groups minus helium . In the elemental form of the p-block elements, the highest energy electron occupies a p-orbital.-See also:...
  
  
• d-block
  D-block
  The d-block is the portion of the periodic table that contains the element groups 3-12. These groups correspond to the filling of the atomic d-orbital subshell, with electron configurations ranging from s2d1 to s2d10...
  
  
• f-block
  F-block
  The f-block of the periodic table of the elements consists of those elements whose atoms or ions have valence electrons in f-orbitals. Actual electronic configurations may be slightly different from what is predicted by the Aufbau principle...
  
  
• g-block (hypothetical)

The block names (s, p, d, f. and g) are derived from the quality of the spectroscopic lines of the associated atomic orbital

Atomic orbital

An atomic orbital is a mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus...

s: sharp, principal, diffuse and fundamental, the rest being named in alphabetical order. Blocks are sometimes called families.

The following is the order for filling the "subshell" orbitals, according to the Aufbau principle

Aufbau principle

The Aufbau principle is used to determine the electron configuration of an atom, molecule or ion. The principle postulates a hypothetical process in which an atom is "built up" by progressively adding electrons...

, which also gives the linear order of the "blocks" (as atomic number increases) in the periodic table:

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, ...

For discussion of the nature of why the energies of the blocks naturally appear in this order in complex atoms, see atomic orbital

Atomic orbital

An atomic orbital is a mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus...

 and electron configuration

Electron configuration

In atomic physics and quantum chemistry, electron configuration is the arrangement of electrons of an atom, a molecule, or other physical structure...

.

The "periodic" nature of the filling of orbitals, as well as emergence of the s, p, d and f "blocks" is more obvious, if this order of filling is given in matrix form, with increasing principal quantum numbers starting the new rows ("periods") in the matrix. Then, each subshell (composed of the first two quantum numbers) is repeated as many times as required for each pair of electrons it may contain. The result is a compressed periodic table, with each entry representing two successive elements:

1s 2s 2p 2p 2p 3s 3p 3p 3p 4s 3d 3d 3d 3d 3d 4p 4p 4p 5s 4d 4d 4d 4d 4d 5p 5p 5p 6s (4f) 5d 5d 5d 5d 5d 6p 6p 6p 7s (5f) 6d 6d 6d 6d 6d 7p 7p 7p

Periodic table

Helium

Helium

Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

 is placed next to hydrogen

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 instead of on top of neon

Neon

Neon is the chemical element that has the symbol Ne and an atomic number of 10. Although a very common element in the universe, it is rare on Earth. A colorless, inert noble gas under standard conditions, neon gives a distinct reddish-orange glow when used in either low-voltage neon glow lamps or...

 because it is part of the s² group. In addition to the blocks listed in this table, there is a hypothetical g-block

G-block

There are currently seven periods in the periodic table of chemical elements, culminating with atomic number 118. If further elements with higher atomic numbers than this are discovered, they will be placed in additional periods, laid out to illustrate periodically recurring trends in the...

 which is not pictured here. g-block

G-block

There are currently seven periods in the periodic table of chemical elements, culminating with atomic number 118. If further elements with higher atomic numbers than this are discovered, they will be placed in additional periods, laid out to illustrate periodically recurring trends in the...

 elements can be seen in the expanded extended periodic table. Also, lutetium and lawrencium

Lawrencium

Lawrencium is a radioactive synthetic chemical element with the symbol Lr and atomic number 103. In the periodic table of the elements, it is a period 7 d-block element and the last element of actinide series...

 are placed under scandium

Scandium

Scandium is a chemical element with symbol Sc and atomic number 21. A silvery-white metallic transition metal, it has historically been sometimes classified as a rare earth element, together with yttrium and the lanthanoids...

 and yttrium

Yttrium

Yttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and it has often been classified as a "rare earth element". Yttrium is almost always found combined with the lanthanides in rare earth minerals and is...

 to reflect their status as d-block

D-block

The d-block is the portion of the periodic table that contains the element groups 3-12. These groups correspond to the filling of the atomic d-orbital subshell, with electron configurations ranging from s2d1 to s2d10...

 elements.

Group Periodic table group In chemistry, a group is a vertical column in the periodic table of the chemical elements. There are 18 groups in the standard periodic table, including the d-block elements, but excluding the f-block elements....  →	1 Alkali metal The alkali metals are a series of chemical elements in the periodic table. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, along with hydrogen. The alkali metals are lithium , sodium , potassium , rubidium , caesium , and francium...	2 Alkaline earth metal The alkaline earth metals are a group in the periodic table. In the modern IUPAC nomenclature, the alkaline earth metals are called the group 2 elements. Previously, they were called the Group IIA elements . The alkaline earth metals contain beryllium , magnesium , calcium , strontium , barium and...	3 Group 3 element The group 3 elements are a group of chemical elements in the periodic table. This group, like other d-block groups, should contain four elements, but it is not agreed what elements belong in the group...	4 Group 4 element The Group 4 elements are a group of chemical elements in the periodic table. In the modern IUPAC nomenclature, Group 4 of the periodic table contains titanium , zirconium , hafnium and rutherfordium . This group lies in the d-block of the periodic table...	5 Group 5 element A Group 5 element is a chemical element in the fifth group in the periodic table. In the modern IUPAC nomenclature, Group 5 of the periodic table contains vanadium , niobium , tantalum and dubnium . This group lies in the d-block of the periodic table...	6 Group 6 element A Group 6 element is one in the series of elements in group 6 in the periodic table, which consists of the transition metals chromium , molybdenum , tungsten , and seaborgium ....	7 Group 7 element A Group 7 element is one in the series of elements in group 7 in the periodic table, which consists of manganese , technetium , rhenium , and bohrium...	8 Group 8 element A Group 8 element is one in the series of elements in group 8 in the periodic table, which consists of the transition metals iron , ruthenium , osmium and hassium ....	9 Group 9 element In modern IUPAC nomenclature, Group 9 of the periodic table contains the elements cobalt , rhodium , iridium , and meitnerium . These are all d-block transition metals...	10 Group 10 element A Group 10 element is one in the series of elements in group 10 in the periodic table, which consists of the transition metals nickel , palladium , platinum , and darmstadtium ....	11 Group 11 element A Group 11 element is one in the series of elements in group 11 in the periodic table, consisting of transition metals which are the traditional coinage metals of copper , silver , and gold...	12 Group 12 element A group 12 element is one of the elements in group 12 in the periodic table. This includes zinc , cadmium and mercury . The further inclusion of copernicium in group 12 is supported by recent experiments on individual Cn atoms...	13 Boron group The boron group is the series of elements in group 13 of the periodic table, comprising boron , aluminium , gallium , indium , thallium , and ununtrium . The elements in the boron group are characterized by having three electrons in their outer energy levels...	14 Carbon group The carbon group is a periodic table group consisting of carbon , silicon , germanium , tin , lead , and ununquadium ....	15 Nitrogen group The nitrogen group is a periodic table group consisting of nitrogen , phosphorus , arsenic , antimony , bismuth and ununpentium ....	16 Chalcogen The chalcogens are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family...	17 Halogen The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...	18 Noble gas The noble gases are a group of chemical elements with very similar properties: under standard conditions, they are all odorless, colorless, monatomic gases, with very low chemical reactivity...
↓ Period Periodic table period In the periodic table of the elements, elements are arranged in a series of rows so that those with similar properties appear in vertical columns. Elements of the same period have the same number of electron shells; with each group across a period, the elements have one more proton and electron...
1 Period 1 element A period 1 element is one of the chemical elements in the first row of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical...
2 Period 2 element A period 2 element is one of the chemical elements in the second row of the periodic table. The periodic table is laid out in rows to illustrate recurring trends in the chemical behavior of the elements as their atomic number increases; a new row is started when chemical behavior begins to...
3 Period 3 element A period 3 element is one of the chemical elements in the third row of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical...
4 Period 4 element A period 4 element is one of the chemical elements in the fourth row of the periodic table of the elements. The periodic table is laid out in rows to illustrate recurring trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour...
5 Period 5 element A period 5 element is one of the chemical elements in the fifth row of the periodic table of the elements. The periodic table is laid out in rows to illustrate recurring trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour...
6 Period 6 element A period 6 element is one of the chemical elements in the sixth row of the periodic table of the elements, including the lanthanides...
7 Period 7 element A period 7 element is one of the chemical elements in the seventh row of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical...
* Lanthanide Lanthanide The lanthanide or lanthanoid series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium... s
** Actinide Actinide The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.The actinide series derives its name from the group 3 element actinium... s