Modern periodic law and Periodic table

PERIODIC TABLE

·      Why do elements are to be classified?

·      It is very difficult to study the chemistry of each and every element

·      Classification of elements enables a better under standing of elements and their properties.

·      The fundamental properties which govern them.

·      Properties of elements repeat periodically like seasons in the nature

·      Atomic number or Electronic configuration is basis for the periodic arrangement of the elements

 MENDELEEV’S PERIODIC TABLE

·      In 1861 Mendeleev for the first time arranged the elements in the increasing of order of their atomic weights in the form of a table

·      He divided the elements into groups (vertical columns) and periods (horizontal rows)

MODERN PERIODIC LAW

·      Mosely (1911) proposed the long form of periodic table

·      The physical and chemical properties of elements are periodic functions of their Atomic Numbers or electronic configurations.

MODERN PERIODIC TABLE

·      It is based on the electronic configurations of the elements.

·      Vertical columns are termed as groups (group I to VIII)

·      Horizontal rows are Periods (Periods 7)

·      All the elements are arranged in the increasing order of their atomic numbers.

CLASSIFICATION OF ELEMENTS INTO BLOCKS

·      There are four blocks in the periodic table these are depends upon the entering of differentiating electron into the sub shell

·      s - block

·      p - block

·      d - block

·      f - block

s-block contains 2 groups 

·      Group 1 – Alkalimetals (ns¹)

·      Group 2 – alkaline earth metals (ns²) 

p-block consists of 6 groups

·      Group – III : Boran family (ns2 np1)

·      Group – IV : Carbon family (ns2 np2)

·      Group – V : Nitrogen family (ns2 np3)

·      Group – VI : Oxygen family (ns2 np4)

·      Group – VII : Halogens (ns2 np5)

·      Group – VIII (or) ‘O’ : Noble gases (ns2 np6) 

d-Block elements consists

·      3d series - from scandium to Zinc

·      4d series - Yttrium to cadmium

·      5d series - hafnium to mercury

·      6d series – actinium …

f-block elementsconsists

·      Lanthanoids – La to Lu

·      Actinoids – Ac to Lr

·      Lanthanoids and actinoids are placed at the bottom of the periodic table in separate blocks.

·      Periodic table consists of 18 groups and 7 periods

·      1st period – 2 elements – shortest period

·      2nd & 3rd periods – 8 elements each – short periods.

·      4th and 5th periods – 18 elements each – Long periods

·      6th periods – 32 elements – Longest period

·      7th period – Incomplete period

CLASSIFICATION OF ELEMENTS BASED ON PROPERTIES

 ·      Noble gas elements or ‘O’ group elements

He, Ne, Ar, Kr, Xe, Rn

·      Representative elements: consists of ‘S’ block and ‘p’ block except ‘0’ group elements

·      Transition elements or ‘d’ block elements

·      Inner transition elements – ‘f’ block elements