MODERN PERIODIC TABLE
GROUPS
· The
vertical columns in the periodic table are called groups or families.
· There
are nine groups in all including viii group consisting of three triads and zero
group of inert gases.
· Groups
I to VII are sub-divided into sub-group A & B.
· Elements
of group IA to group A have their outermost shells incomplete while each of
their inner shell is complete. These elements are called normal or
representative elements. These elements consist of some metals, all non-metals
and metalloids.
· Elements
of groups IB, IIB, IIIB (only Sc, Y, La & Ac), IVB, VB, VIB, VIIB &
VIII have their two outermost shell incomplete. These are called transition
elements. All these are metals.
· Elements
of zero group have all their shells completely filled. These are noble gases.
· Two
groups of 14 elements lying in group IIIB [Ce(z = 58) and Th(z = 90) to Lw(z =
103)] have their three outmost shells incomplete. There are known as
lanthanides and actinides respectively.
PERIODS
· The
horizontal rows in the periodic table are called periods.
· There
are seven periods in the periodic table.
· First
period consist of two elements H & He.
· Second
and third period are 8 elements each.
Second period → from Li to Ne &
3rd period→ from Na to Ar both these are short period.
· Fourth
and fifth periods have 18 elements each.
4th period → from K to
Kr & 5th period → from Rb to Xe. These are long periods.
· Sixth
period has 32 elements from Ca to Rn. It is the longest period. It also
includes 14 lanthanides.
· Seven
period is incomplete. This period also includes 14 actinides. The elements
after U(z = 92) are called transuranic elements. These elements are the result
of atomic research and hence are synthetic elements.
GENERAL CHARACTERISTICS
OF GROUPS
· All
the elements of a given group possess very similar chemical and physical
properties. These are regular gradation in their properties when we move from
top to bottom in a group.
· Size
of atoms increases on descending a group.
· The
metallic character of the elements increases in moving from top to bottom in a
group.
· In
going down a group, the number of electron shells increases by one at each step
and ultimately becomes equal to the number of the period to which the element
belongs.
GENERAL CHARACTERISTICS
OF PERIODS
· Number
of valency electrons increases 1 to 8 as we proceed from left to right in a
period.
· Size
of atoms decreases from left to right in a period.
· From
left to right in a period, metallic character of the element decreases.
DIAGONAL RELATIONSHIP
· Diagonal
relationship is the resemblance of the properties of the elements of 2nd
period with their diagonal opposite members lying in 3rd period.
· Examples
of diagonal relationship found in the periodic table are Li-Mg; Be-Al;B-Si.
DIVISION OF ELEMENTS INTO S-, P-,d-
& f- BLOCK ELEMENTS
S- BLOCK ELEMENTS
· In
the atoms of these electrons, the last electron enter the S-orbit of the
ultimate shell.
· Valence
shell electronic configuration varies from ns1 to ns2.
· Elements
of group IA, group IIA and He belongs to this block.
P-BLOCK ELEMENTS
· In
the atoms of these elements, the last electron enters the p orbit of the
ultimate shell.
· Valence
shell configuration varies from ns2 np1 to ns2
np6.
· Elements
of the group IIIA, IVA, VA, VIA, VIIA & zero group (Ne to Rn) belongs to
this block.
d-BLOCK ELEMENTS
· In
the elements, either in their atomic states or in any of their common oxidation
states, the last electron enter the d-orbit of the penultimate shell i.e. the
last electron goes to the (n-1) d-orbit.
· With
the exceptions of Cr, Cu, Nb, Mo, Ru, Rh, Pd, Ag, Pt & Au, in the atoms of
these elements the ns orbital is completely filled.
Consequently, the valence
shell configuration of these elements varies from (n-1)d1 ns2 (group
IIIB) to (n-1) d10 ns2 (group IIB) configuration.
· The
elements of group IIIB, IVB, VB, VIB, VIII, IB & IIB belong to this block.
· These
elements are classified into four series i.e. 3d, 4d, 5d & 6d orbitals of 3rd,
4th, 5th & 6th shell respectively.
f-BLOCK ELEMENTS
· In
these elements, either in the atomic state or in any of their common oxidation
states, the last electron enters the f-orbit of ante-penultimate shell.
· The
valence shell electron configuration of the
atoms of these elements is represented as: (n-2)ƒ1-7,9-14,
(n-1)d0,1.ns2.
· These
elements are located in group IIIB and have been given a separate place at the
bottom of the periodic table.
· These
are classified into two series i.e 4ƒ and 5ƒ corresponding to the filling of 4ƒ
and 5ƒ orbitals of 4th and 5th shells respectively.
