SUBMITTED BY SUBMITTED TO

NISHA.V.S GISHA.G.R
REG NO:13982011 KUCTE
KULAKKADA


PERIODIC TABLE
The periodic table is a tabular arrangement of the chemical
elements, organized on the basis of their atomic numbers that is the
numbers of protons in the nucleus, electron configurations, and
recurring chemical properties. Elements are presented in order of
increasing atomic number, which is typically listed with
the chemical symbol in each box. The standard form of the table
consists of a grid of elements laid out in 18 columns and 7 rows,
with a double row of elements below that. The table can also be
deconstructed into four rectangular blocks: the s-block to the left,
the p-block to the right, the d-block in the middle, and the f-
block below that.

The rows of the table are called periods; the columns
are called groups, with some of these having names such as
halogens or noble gases. Since, by definition, a periodic table
incorporates recurring trends, any such table can be used to derive
relationships between the properties of the elements and predict
the properties of new, yet to be discovered or synthesized, elements.
As a result, a periodic table whether in the standard form or some
other variant provides a useful framework for analyzing chemical
behavior, and such tables are widely used in chemistry and other
sciences.
Although precursors exist, Dmitri Mendeleev is
generally credited with the publication, in 1869, of the first widely
recognized periodic table. He developed his table to illustrate
periodic trends in the properties of the then-known elements.
Mendeleev also predicted some properties of then-unknown
elements that would be expected to fill gaps in this table. Most of his
predictions were proved correct when the elements in question
were subsequently discovered. Mendeleev's periodic table has since
been expanded and refined with the discovery or synthesis of
further new elements and the development of new theoretical
models to explain chemical behavior.
All elements from atomic numbers 1 to 118 have
been discovered or reportedly synthesized, with elements 113, 115,
117, and 118 having yet to be confirmed. The first 98 elements exist
naturally although some are found only in trace amounts and were
synthesized in laboratories before being found in nature.

Elements
with atomic numbers from 99 to 118 have only been synthesized, or
claimed to be so, in laboratories. Production of elements having
higher atomic numbers is being pursued, with. the question of how
the periodic table may need to be modified to accommodate any
such additions being a matter of ongoing debate. Numerous
synthetic radio nuclides of naturally occurring elements have also
been produced in laboratories.



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Properties 0f periodic table
The properties of the elements exhibit trends or periodicity. These
trends can be predicted using the periodic table and can be
explained and understood by analyzing the electron configurations
of the elements. Elements tend to gain or lose valence electrons to
achieve stable octet formation. Stable octets are seen in the inert
gases, or noble gases, of Group VIII of the periodic table. In addition
to this activity, there are two other important trends. First, electrons
are added one at a time moving from left to right across a period. As
this happens, the electrons of the outermost shell experience
increasingly strong nuclear attraction, so the electrons become
closer to the nucleus and more tightly bound to it. Second, moving
down a column in the periodic table, the outermost electrons
become less tightly bound to the nucleus. This happens because the
number of filled principal energy levels (which shield the outermost
electrons from attraction to the nucleus) increases downward
within each group. These trends explain the periodicity observed in
the elemental properties of atomic radius, ionization energy,
electron affinity, and electronegativity.
Atomic Radius
The atomic radius of an element is half of the distance between the
centers of two atoms of that element that are just touching each
other. Generally, the atomic radius decreases across a period from
left to right and increases down a given group. The atoms with the
largest atomic radii are located in Group I and at the bottom of
groups.
Moving from left to right across a period, electrons are added one at
a time to the outer energy shell. Electrons within a shell cannot
shield each other from the attraction to protons. Since the number
of protons is also increasing, the effective nuclear charge increases
across a period. This causes the atomic radius to decrease.
Moving down a group in the periodic table, the number of electrons
and filled electron shells increases, but the number of valence
electrons remains the same. The outermost electrons in a group are
exposed to the same effective nuclear charge, but electrons are
found farther from the nucleus as the number of filled energy shells
increases. Therefore, the atomic radii increase.
Ionization Energy
The ionization energy, or ionization potential, is the energy required
to completely remove an electron from a gaseous atom or ion. The
closer and more tightly bound an electron is to the nucleus, the
more difficult it will be to remove, and the higher its ionization
energy will be. The first ionization energy is the energy required to
remove one electron from the parent atom. The second ionization
energy is the energy required to remove a second valence electron
from the univalent ion to form the divalent ion, and so on.
Successive ionization energies increase. The second ionization
energy is always greater than the first ionization energy. Ionization
energies increase moving from left to right across a period
(decreasing atomic radius). Ionization energy decreases moving
down a group (increasing atomic radius). Group I elements have low
ionization energies because the loss of an electron forms a stable
octet.
Electron Affinity
Electron affinity reflects the ability of an atom to accept an electron.
It is the energy change that occurs when an electron is added to a
gaseous atom. Atoms with stronger effective nuclear charge have
greater electron affinity. Some generalizations can be made about
the electron affinities of certain groups in the periodic table. The
Group IIA elements, the alkaline earths, have low electron affinity
values. These elements are relatively stable because they have
filled s subshells. Group VIIA elements, the halogens, have high
electron affinities because the addition of an electron to an atom
results in a completely filled shell. Group VIII elements, noble gases,
have electron affinities near zero, since each atom possesses a stable
octet and will not accept an electron readily. Elements of other
groups have low electron affinities. In a period, the halogen will
have the highest electron affinity, while the noble gas will have the
lowest electron affinity. Electron affinity decreases moving down a
group because a new electron would be further from the nucleus of
a large atom.
Electronegativity
Electronegativity is a measure of the attraction of an atom for the
electrons in a chemical bond. The higher the electronegativity of an
atom, the greater its attraction for bonding electrons.
Electronegativity is related to ionization energy. Electrons with low
ionization energies have low electronegativities because their nuclei
do not exert a strong attractive force on electrons. Elements with
high ionization energies have high electronegativities due to the
strong pull exerted on electrons by the nucleus. In a group, the
electronegativity decreases as atomic number increases, as a result
of increased distance between the valence electron and nucleus
(greater atomic radius). An example of an electropositive (i.e., low
electronegativity) element is cesium; an example of a highly
electronegative element is fluorine.
CONCLUSION
The periodic table is one of the most important achievements in the
field of chemistry. It is full of patterns that enable us to better
understand the world around us. Without it, we would not have
many of the products and medicine that we have today.
The information gained from the periodic table can open up
numerous windows of knowledge about the entire universe we live
in. From this activity you should have a much more in depth
understanding of the periodic table.