Block periodic table
each element in a block belong to the same atomic orbital type. Each block is named after its characteristic orbital; thus, the blocks are:
- s-block
- p-block
- d-block
- f-block
- g-block (hypothetical)
The block
names (s, p, d, f and g) are derived from the spectroscopic
notation for the associated atomic orbitals: sharp, principal, diffuse
and fundamental, and then g which follows f in the alphabet.
The following
is the order for filling the "subshell" orbitals, according to
the Aufbau principle, 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 and electron configuration.
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 4f 4f 4f 4f 4f 4f 5d 5d 5d 5d 5d 6p 6p 6p 7s 5f 5f 5f 5f 5f 5f 5f 6d 6d 6d 6d 6d 7p 7p 7p |
The s-block is
on the left side of the periodic table that includes elements from the first
two columns, the alkali metals (group 1) and alkaline earth metals (group 2),
plus helium. Helium is a controversial element for the scientists as it can be
placed in s block as well as p block too but most of the scientists consider it
to be rest at the top of group 18 i.e. above neon(atomic number 10) as it has
many properties similar to the group 18 elements.
Most s-block
elements are highly reactive metals due to the ease with which their outer
s-orbital electrons interact to form compounds. The first period elements in
this block, however, are nonmetals. Hydrogen is highly chemically reactive,
like the other s-block elements, but helium is a virtually unreactive noble
gas.
S-block
elements are unified by the fact that their valence electrons (outermost
electrons) are in the s orbital. The s-orbital is a single spherical cloud
which can contain only one pair of electrons; hence, the s-block consists of
only two columns in the periodic table. Elements in column 1, with a single
s-orbital valence electron, are the most reactive of the block. Elements in the
second column have two s-orbital valence electrons, and, except for helium, are
only slightly less reactive.
p-block
The p-block is
on the right side of the periodic table and includes elements from the six
columns beginning with column 13 and ending with column 18. Helium, though being
in the top of group 18, is not included in the p-block.
The p-block is
home to the biggest variety of elements and is the only block that contains all
three types of elements: metals, nonmetals, and metalloids. Generally, the
p-block elements are best described in terms of element type or group.
P-block
elements are unified by the fact that their valence electrons (outermost
electrons) are in the p orbital. The p orbital consists of six lobed shapes
coming off 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 we reach column 18, which has six
p-orbital electrons.
Metals
P-block metals
have classic metal characteristics: they are shiny, they are good conductors of
heat and electricity, and they lose electrons easily. Generally, these metals
have high melting points and readily react with nonmetals to form ionic
compounds. Ionic compounds form when a positive metal ion bonds with a negative
nonmetal ion.
Of the p-block
metals, several have fascinating properties. Gallium, in the 3rd row of column
13, is a metal that can melt in the palm of a hand. Tin, in the fourth row of
column 14, is an abundant, flexible, and extremely useful metal. It is an
important component of many metal alloys like bronze, solder, and pewter.
Sitting right
beneath tin is lead, a toxic metal. Ancient people used lead for a variety of
things, from food sweeteners to pottery glazes to eating utensils. It has been
suspected that lead poisoning is related to the fall of Roman civilization,[3]
but further research has shown this to be unlikely.[4][5] For a long time, lead
was used in the manufacturing of paints. It was only within the last century
that lead paint use has been restricted due to its toxic nature.
Metalloids
Metalloids have
properties of both metals and nonmetals, but the term 'metalloid' lacks a
strict definition. All of the elements that are commonly recognized as
metalloids are in the p-block: boron, silicon, germanium, arsenic, antimony,
and tellurium. Metalloids tend to have lower electrical conductivity than
metals, yet often higher than nonmetals. They tend to form chemical bonds
similarly to nonmetals, but may dissolve in metallic alloys without covalent or
ionic bonding. Metalloid additives can improve properties of metallic alloys,
sometimes paradoxically to their own apparent properties. Some may give a
better electrical conductivity, higher corrosion resistance, ductility, or
fluidity in molten state, etc. to the alloy.
Boron has many
carbon-like properties, but is very rare. It has many uses, for example a P
type semiconductor dopant.
Silicon is
perhaps the most famous metalloid. It is the second most abundant element in
Earth's crust and one of the main ingredients in glass. It is used to make
microchips for computers and other electronic devices. It is also used in
certain metallic alloys, e.g. to improve casting properties of alumimium. So
valuable is silicon to the technology industry that Silicon Valley in California
is named after it.
Germanium has
properties very similar to silicon, yet this element is much more rare. It was
once used for its semiconductor properties pretty much as silicon is now, and
it has some superior properties at that, but is now a rare material in the
industry.
Arsenic is a
toxic metalloid that has been used throughout history as an additive to metal
alloys, paints, and even makeup.
Antimony is
used as a constituent in casting alloys such as printing metal.
Not always
considered as metalloids:
Carbon, in the
same column with silicon and germanium, electrically fairly conductive unlike
most other nonmetals, and to an extent preferred as a trace constituent in
certain metallic alloys such as steel
Phosphorus has
metallurgical uses among others, e.g. a constituent of some copper alloys
Selenium, once
used as a semiconductor material, and also used to improve properties of
metallic alloys
Aluminium is
generally considered a metal, but it has some metalloid/non-metal properties
such as negative oxidation states
Noble
gases
Previously
called inert gases, their name was changed as there are a few other gases that
are inert but not noble gases, such as nitrogen. The noble gases are located in
the far right column of the periodic table, also known as Group Zero or Group
Eighteen. Noble gases are also called as aerogens but this nomenclature of the
group is not officially accepted by the IUPAC.
All of the
noble gases have full outer shells with eight electrons. However, at the top of
the noble gases is helium, with a shell that is full with only two electrons.
The fact that their outer shells are full means they rarely react with other
elements, which led to their original title of "inert."
Because of
their chemical properties, these gases are also used in the laboratory to help
stabilize reactions that would usually proceed too quickly. As the atomic
numbers increase, the elements become rarer. They are not just rare in nature,
but rare as useful elements, too.
Helium is best
known for its low density, used to safely produce buoyancy for zeppelins and
balloons
Neon is
notorious as the red to yellow glow medium of old low power signal lamps and
signs
Argon is used
as a protective gas in MIG and TIG welding
Xenon is used
as a plasma medium in high intensity arc lamps with tungsten electrodes.
Automotive xenon lights, however, are mostly mercury vapor bulbs with low
pressure xenon to help striking the arc and producing light instantly.
Krypton has
many uses like arc flash medium. Krypton filled incandescent bulbs were once
the most efficient variety, before being replaced by halogen technology.
Radon is
radioactive, and one of the densest elements to remain in gas state at room
temperature
Halogens
The second
column from the right side of the periodic table, group 17, is the halogen
family of elements. These elements are all just one electron shy of having full
shells. Because they are so close to being full, they have the trait of
combining with many different elements and are very reactive. They are often
found bonding with metals and elements from Group One, as these elements in
each have one electron.
Not all
halogens react with the same intensity. Fluorine is the most reactive and
combines with most elements from around the periodic table. As with other
columns, reactivity decreases as the atomic number increases.
When a halogen
combines with another element, the resulting compound is called a halide. One
of the best examples of a halide is sodium chloride (NaCl).
d-block
The d-block is
on the middle of the periodic table and includes elements from columns 3
through 12. These elements are also known as the transition metals because they
show a transitivity in their properties i.e. they show a trend in their
properties
The d-block
elements are all metals which exhibit two or more ways of forming chemical
bond. 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. This results in the same element exhibiting two or
more oxidation states, which determines the type and number of its nearest
neighbors in chemical compounds.
D-block
elements are unified by having in their outermost electrons one or more
d-orbital electrons but no p-orbital electrons. The d-orbitals can contain up
to five pairs of electrons; hence, the block includes ten columns in the
periodic table.
f-block
The f-block is
in the center-left of a 32-column periodic table but in the footnoted appendage
of 18-column tables. These elements are not generally considered as part of any
group. They are often called inner transition metals because they provide a
transition between the s-block and d-block in the 6th and 7th row (period), in
the same way that the d-block transition metals provide a transitional bridge
between the s-block and p-block in the 4th and 5th rows.
The known
f-block elements come in two series, the lanthanides of period 6 and the
radioactive actinides of period 7. All are metals. Because the f-orbital
electrons are less active in determining the chemistry of these elements, their
chemical properties are mostly determined by outer s-orbital electrons.
Consequently, there is much less chemical variability within the f-block than
within the s-, p-, or d-blocks.
F-block
elements are unified by having one or more of their outermost electrons in the
f-orbital but none in the d-orbital or p-orbital. The f-orbitals can contain up
to seven pairs of electrons; hence, the block includes fourteen columns in the
periodic table.
g-block
The g-block is
a hypothetical block of elements in the extended periodic table whose outermost
electrons are posited to have one or more g-orbital electrons but no f-, d- or
p-orbital electrons.
Source: Wikipedia
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