THE TYPES OF ELEMENTS

 Using electronic    configuration as the criterion ,we ordinarily recognise four general type of elements ;

1. The inert gas elements 
2. THe representative elements 
3. The transition elements 
4. The inner transition elements.

"The classification of these elements into these groups is dependent on the extent to which the s,p,d and f orbitals are filled".

(1) Inert Gases

(a) s and p _orbital of the most shell of these elements are completely filled. The outermost electronic configuration in ns2np6.

(b) HElium is also inert but it's electronic configuration is 1s2.

(2) Representative or normal elements:-

(a) Outermost shell of these elements is incomplete. The number of electrons is the outermost shell is less than eight.

(b) Inner shells are complete.

(c) s-  and p-block  elements except inert gases are called normal or representative elements.

(3) Transition Elements ;

(a) Last two shells of these elements namely outermost and penultimate shells are incomplete.

(b) The last shell contain one or two electrons and the penultimate shell may contain more than upto eighteen electrons.

(c) The outermost electronic configuration is similar to d-block elements,i.e.,(n-1)d¹-¹⁰ ns¹-².

(d) According to latest defination of transition elements those elements which have partly filled d-orbitals in neutral state or in any stable oxidation are called transition elements. 

"According to this defination, 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 state.

(e) Because of the extra stability which is associated with empty, half filled, and 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

(4)Inner transition elements:-

(a)In these elements last three shells i.e.,last ,penultimate and prepenultimate shells are incomplete.

(b) These are related to IIB 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 outermost electronic confiiguration is similar to f-block element i.e.,(n-2)f¹-14(n-1)s²(n-1)s²(n-1)p⁶(n-1)d⁰-¹ ns².