Types of ELEMENTS | Additional Study Material for JEE PDF Download

Using electronic configuration as the criteria, we generally recognize four general type of elements; the inert
gas elements, the representative elements, the transition elements, and the inner transition elements. The
classification of the elements into these groups is dependent on the extent to which the s, p, d and f orbitals are
filled.
Inert Gases
(a) s and p orbitals of the outer most shell of these elements are completely filled. The outermost electronic
configuration is ns2
np6
.

(b) Helium is also inert gas but its electronic configuration is 1s2
Representative or Normal Elements
(a) Outermost shell of these elements is incomplete. The number of electrons in the outermost shell is less
than eight.
(b) Inner shell are complete.
(c) s-and p-block elements except inert gases are called normal or representative elements.
Transition Elements
(a) Last two shells of these elements namely outermost and penultimate shells are incomplete.
(b) The last shell contains one or two electrons and the penultimate shell may contain more than eight or up
to eighteen electrons.
(c) Their outermost electronic configuration is similar to d-block elements i.e. (n–1) d1-10 ns1-2.
(d) According to definition of transition elements, those elements which have partly filled d-orbitals in neutral
state or in any stable oxidation state are called transition elements. According to this definition Zn, Cd and
Hg (IIB group) are d-block elements but not transition elements because these elements have d10
configuration in neutral as well as in stable +2 oxidation state.
(e) Because of the extra stability which is associated with empty, half-filled, and fully filled subshells, there
are some apparent anomalies in electronic arrangements in the transition series. This empirical rule is
illustrated by the chromium and copper configuration in the first d series of elements:
           Sc  Ti  V   Cr   Mn  Fe  Co  Ni   Cu   Zn
3d       1    2    3    5     5     6    7     8       10   10
4s        2   2    2    1      2     2    2     2        1     2

Inner Transition Elements
(a) In these elements last three shells i.e. last, penultimate and prepenultimate shells are incomplete.
(b) These are related to IIIB i.e. group 3.

(c) The last shell contains two electrons. Penultimate shell may contain eight or nine electrons and pre-
penultimate shell contains more than 18, up to 32 electrons.

(d) Their outemost electronic configuration is similar to f-block element i.e. (n-2)f1-14 (n-1)s2 (n-1)p6 (n-1)d0-1ns2
Determination of period, block and group of an element
(a) Period number: The period no. of the element can be predicted from the principal quantum no. (n) of
the valence shell.
(b) Block number: Last electron enter in which orbital is knows as block no. .
(c) Group number: It is predicted from the number of electrons in the valence shell and penultimate shell.
Example :

S.No.      Electronic        Period       Block       Prediction          Group
              Configuration     number  number       of Group        number

1.       [Ar]4s2 3d104p65s1  5             s               No. of ns e–        1

2.      [Kr] 5s24d105p2        5           p           (ns e–+ 10 + np e–)  2+10+2 =14

3.       [Xe] 6s25d14f12        6           f                 —                            3/III B