LONG FORM OF PERIODIC TABLE

                              LONG FORM OF PERIODIC TABLE

            Bohr's in 1920 modified the modern periodic table which is named  as long form of periodic table. Hence, it is an improved and extended  form of mendeleev's periodic table and is based on the modern periodic law. It states  that ," the physical and chemical properties of an electron are periodic function of their atomic number."

                Bohr's classification of elements in the periodic table divides the all known elements into different groups and subgroups. According to this classification left portion of periodic table consist of highly electropositive metal, elements right portion consists of highly electronegative known metal, some heavy metals and metalloids and the middle portion consists of transition and inner transition elements.

SIGNIFICANCE OF LONG FORM OF PERIODIC TABLE

Long form of periodic table removes some serious  drawbacks in mendeleev's periodic table and attains superior position in the classification. Some of the significance are;

1.       The arrangement of  element is based on a more fundamental basis, atomic number.

2.       The position of element in certain group or period is related to the electronic  configuration of its atom.

3.       It gives the complete separation between metals and non- metals.

4.       It is divided into four blocks depending upon the valence shell configuration of an atom such as  s,p,d,f   block.

5.       Due the separation of groups into sub-groups, dissimilar elements fall on the different group such as alkali metal and coinage metal.

6.       The position of transition metal element and inner transition metal element is suitable  due to their transitional behavior between s -block and p- block elements.                                                                                       

               DRAWBACKS/LIMITATION

Although it removes more drawbacks of mendeleev's periodic table but yet suffer from the following defects;

1.       Position of Hydrogen;

The position of hydrogen in this periodic table has not been solved completely since the valence shell configuration is same as that of alkali metals but the properties have completely different.

2.       Position of Hellium;

Since the Hellium has the same electronic configuration with alkali earth metal but the properties are similar to nobal gases even the configuration is different.

3.       Position of Lanthanides and Actinides

The Lanthanides and Actinides are given a separate place below the periodic table but can not include in the main body of periodic table.