What is The Periodic Table ?
Periodic table is a table in which the chemical elements
are arranged in order of their atomic numbers. With this
arrangement, elements with similar chemical properties and
electronic structures are displayed as vertical columns
of the table.
Why are elements with similar properties recurring
in Periodic Table ?
The electrons in the outermost shell of an atom control
its chemical properties as they determine what type
of reaction they undergo. When elements are arranged
in the periodic table, the elements having same number
of valence electrons (no.of electrons in the outermost
shell) come under each other forming a group. Thus
elements in the same group have similar chemical properties.
Relevant Terminology :
Periods : The horizontal rows in
the periodic table are called periods. Elements in
the same period have the same number of shells but
the number of electrons increases by 1 for each element.
Groups : The vertical columns in
the periodic table are called groups. Elements in
a group have the same number of valence electrons
but the no. of shells increases by 1 for each element.
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Atomic Size(Radii) - The radius of an
atom may be taken as the distance between the the nucleus
of the atom and the outermost shell.
Atomic size increases down the group and decreases
across a period.
Francium has the largest atomic size.
Ionization Potential - It is the amount
of energy absorbed when one electron is removed from the
outermost shell of an isolated gaseous atom.
IP increases across a period and decreases down
the group.
Fluorine has the highest I.P.
Electron Affinity - It is the amount of
energy released when one electron is added to the outermost
shell of an isolated gaseous atom.
It increases across a period and decreases down
the group.
Chlorine has the highest electron affinity.
Electronegativity - The tendency of an
atom to attract the shared pair of electrons towards itself
when combined in a compound is called electronegativity.
It increases across a period and decreases down
the group.
Fluorine has the highest electronegativity.
Metallic and non metallic character -
An element is considered as a metal if it loses electrons
when supplied with energy. When an element gains electrons
it is said to be a non metal.
Metallic character increases down the group.
Non-metallic character increases across a period.
Caesium is the most metallic element.
Important Groups :
Few groups of elements are important from the students
point of view. A brief study on selected groups can be found
here. Some of the groups have been assigned special
names.
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Coinage Elements : Copper,Silver and Gold
make up Group 11 of the periodic table. These are so called
because they are used for making coins.
Transition Metals : There are 21 metals
in this group, which includes columns 4 to 10, the central
block of the periodic table. They fall in three periods
of the table: from titanium to nickel, from zirconium to
palladium, and from hafnium to platinum.
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