A block of the
periodic table
The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of ...
is a set of elements unified by the
atomic orbitals their
valence electrons
In chemistry and physics, a valence electron is an electron in the outer shell associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed. In a single covalent bond, a shared pair fo ...
or vacancies lie in.
The term appears to have been first used by
Charles Janet
Charles Janet (; 15 June 1849 – 7 February 1932) was a French engineer, company director, inventor and biologist. He is also known for his innovative ''left-step'' presentation of the periodic table of chemical elements.
Life and work
Janet gra ...
. Each block is named after its characteristic orbital: s-block, p-block, d-block, and f-block.
The block names (s, p, d, and f) are derived from the
spectroscopic notation for the value of an electron's
azimuthal quantum number
The azimuthal quantum number is a quantum number for an atomic orbital that determines its angular momentum operator, orbital angular momentum and describes the shape of the orbital. The wikt:azimuthal, azimuthal quantum number is the second of ...
: sharp (0), principal (1), diffuse (2), or fundamental (3). Succeeding notations proceed in alphabetical order, as g, h, etc., though elements that would belong in such blocks have not yet been found.
Characteristics
There is an ''approximate'' correspondence between this nomenclature of blocks, based on
electronic configuration, and sets of elements based on chemical properties. The s-block and p-block together are usually considered
main-group elements, the d-block corresponds to the
transition metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that c ...
s, and the f-block corresponds to the inner transition metals and encompasses nearly all of the
lanthanide
The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and y ...
s (like
lanthanum) and the
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 first element in the series, actinium. The inf ...
s (like
actinium).
The
group 12 elements
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic t ...
,
cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
, and
mercury are sometimes regarded as main group, rather than transition group, because they are chemically and physically more similar to the p-block elements than the other d-block elements. The
group 3 elements are occasionally considered main group elements due to their similarities to the s-block elements. However, they remain d-block elements even when considered to be main group.
Groups (columns) in the f-block (between groups 2 and 3) are not numbered.
Helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
is an
s-block
A block of the periodic table is a set of elements unified by the atomic orbitals their valence electrons or vacancies lie in. The term appears to have been first used by Charles Janet. Each block is named after its characteristic orbital: s-b ...
element, with its outer (and only) electrons in the 1s
atomic orbital
In atomic theory and quantum mechanics, an atomic orbital is a function describing the location and wave-like behavior of an electron in an atom. This function can be used to calculate the probability of finding any electron of an atom in an ...
, although its chemical properties are more similar to the p-block
noble gas
The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low che ...
es in group 18 due to its full shell.
s-block
The s-block, with the s standing for "sharp" and
azimuthal quantum number
The azimuthal quantum number is a quantum number for an atomic orbital that determines its angular momentum operator, orbital angular momentum and describes the shape of the orbital. The wikt:azimuthal, azimuthal quantum number is the second of ...
0, is on the left side of the conventional periodic table and is composed of elements from the first two columns plus one element in the rightmost column, the nonmetals
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
and
helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
and the
alkali metals (in group 1) and
alkaline earth metal
The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).. The elements have very similar properties: they are ...
s (group 2). Their general valence configuration is ''n''s
1–2.
Helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
is an s-element, but nearly always finds its place to the far right in
group 18, above the p-element
neon
Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypt ...
. Each
row
Row or ROW may refer to:
Exercise
*Rowing, or a form of aquatic movement using oars
*Row (weight-lifting), a form of weight-lifting exercise
Math
*Row vector, a 1 × ''n'' matrix in linear algebra.
*Row (database), a single, implicitly structured ...
of the table has two s-elements.
The metals of the s-block (from
the second period onwards) are mostly soft and have generally low melting and boiling points. Most impart colour to a flame.
Chemically, all s-elements except
helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
are highly reactive. Metals of the s-block are highly electropositive and often form essentially ionic compounds with nonmetals, especially with the highly electronegative halogen nonmetals.
p-block
The p-block, with the p standing for "principal" and azimuthal quantum number 1, is on the right side of the standard periodic table and encompasses elements in groups 13 to 18. Their general electronic configuration is ''n''s
2 ''n''p
1–6.
Helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
, though being the first element in group 18, is not included in the p-block. Each row of the table has a place for six p-elements except for
the first row (which has none).
This block is the only one having all three types of elements:
metal
A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typi ...
s,
nonmetal
In chemistry, a nonmetal is a chemical element that generally lacks a predominance of metallic properties; they range from colorless gases (like hydrogen) to shiny solids (like carbon, as graphite). The electrons in nonmetals behave differen ...
s, and
metalloids. The p-block elements can be described on a group-by-group basis as: group 13, the ''
icosagens''; 14, the ''
crystallogens''; 15, the ''
pnictogens''; 16, the ''
chalcogens''; 17, the ''
halogens
The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this group ...
''; and 18, the ''
helium group'', composed of the ''
noble gases
The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low ch ...
'' (excluding helium) and
oganesson. Alternatively, the p-block can be described as containing ''
post-transition metals
The metallic elements in the periodic table located between the transition metals and the chemically weak nonmetallic metalloids have received many names in the literature, such as ''post-transition metals'', ''poor metals'', ''other metals'', ...
''; ''metalloids''; ''
reactive nonmetals'' including the ''halogens''; and ''noble gases'' (excluding helium).
The p-block elements are unified by the fact that their valence (outermost) electrons are in the p orbital. The p orbital consists of six lobed shapes coming from a central point at evenly spaced angles. The p orbital can hold a maximum of six electrons, hence there are six columns in the p-block. Elements in column 13, the first column of the p-block, have one p-orbital electron. Elements in column 14, the second column of the p-block, have two p-orbital electrons. The trend continues this way until column 18, which has six p-orbital electrons.
The block is a stronghold of the
octet rule
The octet rule is a chemical rule of thumb that reflects the theory that main-group elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas. The ...
in its first row, but elements in subsequent rows often display
hypervalence. The p-block elements show variable oxidation states usually differing by multiples of two. The reactivity of elements in a group generally decreases downwards. (Helium breaks this trend in group 18 by being more reactive than neon, but since helium is actually an s-block element, the p-block portion of the trend remains intact.)
The bonding in between metals and nonmetals depends on the electronegativity difference. Ionicity is possible when the electronegativity difference is high enough (e.g.
Li3N). Metals in high oxidation states tend to form covalent structures (e.g.
WF6), as do the more noble metals (e.g.
HgCl2). There are also some metal oxides displaying
electrical (metallic) conductivity, like
RuO2,
ReO3, and
IrO2. The metalloids tend to form either covalent compounds or alloys with metals.
d-block
The d-block, with the d standing for "diffuse" and azimuthal quantum number 2, is in the middle of the periodic table and encompasses elements from groups 3 to 12; it starts in the
4th period. Periods from the fourth onwards have a space for ten d-block elements. Most or all of these elements are also known as
transition metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that c ...
s because they occupy a transitional zone in properties, between the strongly electropositive metals of groups 1 and 2, and the weakly electropositive metals of groups 13 to 16. Group 3 or group 12, while still counted as d-block metals, are sometimes not counted as transition metals because they do not show the chemical properties characteristic of transition metals as much, for example, multiple
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. ...
s and coloured compounds.
The d-block elements are all metals and most have one or more chemically active d-orbital electrons. Because there is a relatively small difference in the energy of the different d-orbital electrons, the number of electrons participating in chemical bonding can vary. The d-block elements have a tendency to exhibit two or more oxidation states, differing by multiples of one. The most
common oxidation states are +2 and +3.
Chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal.
Chromium metal is valued for its high corrosion resistance and h ...
,
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...
,
molybdenum
Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with le ...
,
ruthenium
Ruthenium is a chemical element with the symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most other chemic ...
,
tungsten
Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isol ...
, and
osmium can have formal oxidation numbers as low as −4;
iridium holds the singular distinction of being capable of achieving an oxidation state of +9.
The d-orbitals (four shaped as
four-leaf clover
The four-leaf clover is a rare variation of the common three-leaf clover. According to traditional sayings, such clovers bring good luck, though it is not clear when or how this idea began. One early mention of "Fower-leafed or purple grasse" i ...
s, and the fifth as a
dumbbell
The dumbbell, a type of free weight, is a piece of equipment used in weight training. It can be used individually or in pairs, with one in each hand.
History
The forerunner of the dumbbell, halteres, were used in ancient Greece as lifting ...
with a ring around it) can contain up to five pairs of electrons.
f-block
The f-block, with the f standing for "fundamental" and azimuthal quantum number 3, appears as a footnote in a standard 18-column table but is located at the center-left of a 32-column full width table. Periods from the sixth onwards have a place for fourteen f-block elements. While these elements are generally not considered part of any
group, some authors consider them to be part of group 3. They are sometimes called
inner transition metal
A block of the periodic table is a set of elements unified by the atomic orbitals their valence electrons or vacancies lie in. The term appears to have been first used by Charles Janet. Each block is named after its characteristic orbital: s-blo ...
s because they provide a transition between the s-block and d-block in the
6th
6 (six) is the natural number following 5 and preceding 7. It is a composite number and the smallest perfect number.
In mathematics
Six is the smallest positive integer which is neither a square number nor a prime number; it is the second small ...
and
7th row (period), in the same way that the d-block
transition metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that c ...
s provide a transitional bridge between the s-block and p-block in the 4th and 5th rows.
The f-block elements come in two series, in periods 6 and 7. All are metals. The f-orbital electrons are less active in the chemistry of the period 6 f-block elements, although they do make some contribution: these are rather similar to each other. They are more active in the early period 7 f-block elements, where the energies of the 5f, 7s, and 6d shells are quite similar; consequently these elements tend to show as much chemical variability as their transition metals analogues. The later f-block elements behave more like their period 6 counterparts.
The f-block elements are unified by mostly having one or more electrons in an inner f-orbital. Of the f-orbitals, six have six lobes each, and the seventh looks like a dumbbell with a donut with two rings. They can contain up to seven pairs of electrons hence the block occupies fourteen columns in the periodic table. They are not assigned group numbers, since vertical periodic trends cannot be discerned in a "group" of two elements.
The two 14-member rows of the f-block elements are sometimes confused with the ''
lanthanides'' and the ''
actinides'', which are names for sets of elements based on chemical properties more so than electron configurations. The lanthanides are the 15 elements running from
lanthanum (La) to
lutetium (Lu); the actinides are the 15 elements running from
actinium (Ac) to
lawrencium (Lr).
g-block
A g-block, with azimuthal quantum number 4, is predicted to begin in the vicinity of
element 121. Though g-orbitals are not expected to start filling in the ground state until around element
124–
126 126 may refer to:
*126 (number), a natural number
*AD 126, a year in the 2nd century AD
*126 BC, a year in the 2nd century BC
*126 film, a cartridge-based film format used in still photography
* 126 (New Jersey bus)
* 126 Artist-run Gallery
*Interst ...
(see
extended periodic table), they are likely already low enough in energy to start participating chemically in element 121,
similar to the situation of the 4f and 5f orbitals.
If the trend of the previous rows continued, then the g-block would have eighteen elements. However, calculations predict a very strong blurring of periodicity in the eighth period, to the point that individual blocks become hard to delineate. It is likely that the eighth period will not quite follow the trend of previous rows.
See also
*
Electron shell subshells
References
External links
The tetrahedral periodic table of elements Animation showing a transition from the conventional table into a tetrahedron.
{{DEFAULTSORT:Block
Periodic table
Sets of chemical elements