Periodic Properties - Long form of the Periodic Table and Electronic Configuration of elements - Moseley's Periodic Table

Long form of the Periodic Table and Electronic Configuration of elements 

Many different forms of a periodic classification of the elements have appeared since the 1871 table by Mandeleef. Each table was designed to point up the various trends and relationship which its author considered most significant. From the literally hundreds of tables which have been proposed,perhaps the most popular and easily reproduced periodic table is the conventional extended or long form, which is shown in table.

i)  Each period starts with an alkali metal whose outermost electronic configuration is ns1.

ii)  Each period ends with a noble gas of outermost electronic configuration ns2np6 except He. The electronic configuration of He is 1s2.


iii)  The number of elements in a period is equal to the number of necessary electrons to acquire ns2np6 configuration in the outermost shell of first element (alkali metal) of the period. First period contains two elements.

iv) The number of elements in each period may be determined by the number of electrons in a stable configuration as under

The number of elements in each period may be determined by the number of electrons in a stable configuration as under

Electronic basis for the periodic classification

  • With a better understanding of the part that the electron plays great role in the properties of the elements, a corresponding understanding of the periodic system came about.
  • On the basis of electronic configuration, the elements may be divided into four groups.

 

i)  s-Block elements


a)  These are present in the left part of the periodic table.


b)  These are IA and IIA i.e. 1 and 2 group elements.


c)  These are metals.


d)  In these elements last electron fills in the s-orbital.


e)  Electronic configuration of valence shell is ns1-2 ( n = 1 to 7).

ii)  p – block elements


a)  These are present in right part of the periodic table.


b)  These constitute the groups IIIA to VIIA and zero groups i.e. groups 13 to 18 of the periodic table.


c)  Most of these elements are metalloids and non metals but some of them are metals also.


d)  The last electron fills in p-orbital of valence shell.


e)  The electronic configuration of valence shell is ns2np1-6 ( n = 2 to 7).


f)  ns2np6is stable noble gas configuration. The electronic configuration of He 1s2.

iii) d-Block elements


a)  These are present in the middle part of the periodic table (between s & p block elements.


b)  These constitute IIIB to VIIB, VIII, IB and IIB i.e, 3 to 12 groups of the periodic table.


c)  All are metals.

d)  The last electrons fill in ( n – 1)d orbital.


e)  The outermost electronic configuration is 


f)  There are three series of d-block elements as under:

3d series – Sc(21) to Zn (30)
4d series – Y (39) to Cd (48)
5d series – La (57), Hf (72) to Hg (80)

iv) f-Block elements

 

These are placed separately below the main periodic table.

These are mainly related to IIIB i.e. group 3 of the periodic table.

There are two series of -block elements as under:

4f series – Lanthanides – 14 Elements from Ce (58) to Lu (71)

5f series – Actinides – 14 Elements from Th (90) to Lw (103)

The last electron fills in ( n – 2) -orbital

Their outermost electronic configuration is 

 

Post By : Rahul Kumar 12 Mar, 2020 1846 views Chemistry