Page 147 - Chemistry ICSE Class IX
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The Periodic Table 135
Metallic character of an element is related to its electron-losing
tendency. The element which has a greater tendency to lose electrons
is more metallic. For example, in group IVA, carbon (C), its rst
member is a nonmetal. The metallic character increases in going from
top to bottom. As a result, the last member of this group, i.e., lead (Pb)
is a typical metal. By the same logic, cesium (Cs) is the most metallic
and lithium (Li) is the least of all the alkali metals.
Nonmetallic character of elements in a group decreases as we go
down the group. Thus, in any group, the element at the top is the Group VII
most nonmetallic and that at the bottom is the least nonmetallic. For EŽŶŵĞƚĂůůŝĐ &ůƵŽƌŝŶĞ ;&Ϳ
example, in the halogen group (Group VIIA), fluorine (F) is the most ĐŚĂƌĂĐƚĞƌ
nonmetallic and iodine (I) is the least nonmetallic. ĚĞĐƌĞĂƐĞƐ ŚůŽƌŝŶĞ ; ůͿ
ĚŽǁŶ ƚŚĞ ƌŽŵŝŶĞ ; ƌͿ
Nonmetallic character of an element is related to its tendency to ŐƌŽƵƉ
accept/gain electron. The tendency to gain electron decreases with /ŽĚŝŶĞ ;/Ϳ
an increase in the atomic size. Therefore, the nonmetallic character of
elements in a group decreases down the group.
How do the metallic character and nonmetallic character
vary in a period
The tendency of an atom to lose electrons decreases in a period from left
to right. Therefore, the metallic character decreases in going from left to
right in a period. Thus, the elements on the left side of the periodic table are
the most metallic.
For the same reason, nonmetallic character increases in going from
left to right in a period. Therefore, the elements on the right side of the
periodic table are the most nonmetallic.
Period 2 Li Be B C N O F Ne
Period 3 Na Mg Al Si P S Cl Ar
metallic character decreases
Metals o Nonmetals
nonmetallic character increases
Chemical Reactivity
Chemical properties of an element are largely governed by its valence
electrons. That is why, all elements of a group show similar chemical
properties. However, there is a slight variation in the reactivity of the
elements in a group. For example,
For metallic elements, the reactivity increases in going from top to
bottom in a group. Thus, the reactivity of alkali metals (elements of
Group 1) follows the order,
Cs > Rb > K > Na > Li Sand mainly consists of
—— Reactivity decreases in this direction o silicon dioxide
For nonmetallic elements, the reactivity decreases in going from top
to bottom in a group. The reactivity of the halogen group elements
(Group 17) varies as follows:
F > Cl > Br > I
—— Reactivity decreases o
All group 0 elements (noble gases) are nonreactive. This is because
these elements have their outermost shell completely lled. As a result,
atoms of these elements show no tendency to lose or gain electrons.
